Fix build with Boost + Python 3.7.

Taken from upstream:
https://github.com/ukoethe/vigra/commit/a6fa62663c6a6b752ed0707e95f643e25867a0f9

diff --git a/vigranumpy/src/core/vigranumpycore.cxx b/vigranumpy/src/core/vigranumpycore.cxx
index ec38d3636..c81c6ae52 100644
--- a/vigranumpy/src/core/vigranumpycore.cxx
+++ b/vigranumpy/src/core/vigranumpycore.cxx
@@ -61,7 +61,7 @@ UInt32 pychecksum(python::str const & s)
 	return checksum(data, size);
 #else
 	Py_ssize_t size = 0;
-	char * data = PyUnicode_AsUTF8AndSize(s.ptr(), &size);
+	const char * data = PyUnicode_AsUTF8AndSize(s.ptr(), &size);
 	return checksum(data, size);
 #endif
 }
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<div class='path'>path: <a href='/guix/log/?id=4f837f30454e4b4f81d567054f077461155c92dd&amp;showmsg=1'>root</a>/<a href='/guix/log/.mailmap?id=4f837f30454e4b4f81d567054f077461155c92dd&amp;showmsg=1'>.mailmap</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/.mailmap?id=4f837f30454e4b4f81d567054f077461155c92dd'>Collapse</a>)</th><th class='left'>Author</th></tr>
<tr class='logheader'><td><span title='2024-08-05 00:44:43 +0300'>2024-08-05</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=3c309a7b7020a9645bfe775d9f53f43f05d076bf'>Change email of Evgeny Pisemsky.</a></td><td>Evgeny Pisemsky</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* .mailmap: Add entry to Evgeny Pisemsky.
* gnu/packages/emacs-xyz.scm, gnu/packages/engineering.scm,
gnu/packages/guile-xyz.scm, gnu/packages/hardware.scm,
gnu/packages/perl.scm, gnu/packages/python-xyz.scm,
gnu/packages/sdl.scm, gnu/packages/web.scm: Adjust copyright line.

Change-Id: I9a10be1ee7cc164f18d826b51348ee26eee2ca4b
Signed-off-by: Efraim Flashner &lt;efraim@flashner.co.il&gt;


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<tr class='logheader'><td><span title='2024-01-07 19:07:18 +0100'>2024-01-07</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=7b58443bc5506a56ea78aaf44006ce6209ee6cc8'>Update mailmap.</a></td><td>Tomas Volf</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* .mailmap: Add entry for Tomas Volf.

Change-Id: I0a8b43b3b7f71c3020f96118adcbad8937a290fb
Signed-off-by: Mathieu Othacehe &lt;othacehe@gnu.org&gt;


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<tr class='logheader'><td><span title='2023-08-16 22:22:06 +0200'>2023-08-16</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=fce924708c31c09a1b438ae7e8b83d39c492be9a'>Update email addresses for Juliana Sims.</a></td><td>Juliana Sims</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* .mailmap: Add an entry for Juliana.
* gnu/packages/admin.scm, gnu/packages/audio.scm,
gnu/packages/build-tools.scm, gnu/packages/scheme.scm: Update Juliana's email.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;


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<tr class='logheader'><td><span title='2022-01-11 14:48:00 -0500'>2022-01-11</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=7f779286df7e8636d901f4734501902cc934a72f'>Update mailmap.</a></td><td>Leo Famulari</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* .mailmap: Add entry for Zheng Junjie.


</td></tr>
<tr class='logheader'><td><span title='2021-11-06 16:03:43 +0100'>2021-11-06</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=567c4f4495fd1681bc6bd1ca3e9d1a87e120ac61'>Update mailmap and copyright assignments for Liliana Marie Prikler.</a></td><td>Liliana Marie Prikler</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
Use full names everywhere.

* .mailmap: Use full name for Liliana Marie Prikler.
* gnu/packages/zig.scm: Likewise.


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<tr class='logheader'><td><span title='2021-09-06 12:15:57 +0200'>2021-09-06</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=7158f8e4e9f81dbe004789018dcf06a5fe87d602'>Update mailmap.</a></td><td>Liliana Marie Prikler</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* .mailmap: Add entry for Liliana Marie Prikler.


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<tr class='logheader'><td><span title='2021-09-04 12:25:17 +0200'>2021-09-04</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=1fd0bf60ea261fac426052386029ead0ac68cad1'>Update mailmap.</a></td><td>Marius Bakke</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* .mailmap: Alias all my contributions to the same identity.


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<tr class='logheader'><td><span title='2021-07-27 12:34:56 -0400'>2021-07-27</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=c0e6e8d25e3750a35bebc80469ee86e7826bd769'>Update mailmap.</a></td><td>Leo Famulari</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* .mailmap: Add entry for Christine Lemmer-Webber.


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<tr class='logheader'><td><span title='2021-07-08 09:48:22 +0200'>2021-07-08</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=0a04c25482c4d848a6a29711fccf5682319e26aa'>mailmap: Update entries for Matthew James Kraai.</a></td><td>Matthew James Kraai</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* .mailmap: Change name for Matthew James Kraai.
* gnu/packages/lisp-xyz.scm, gnu/packages/python-xyz.scm,
gnu/packages/rust.scm: Likewise.

Signed-off-by: Nicolas Goaziou &lt;mail@nicolasgoaziou.fr&gt;


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<tr class='logheader'><td><span title='2021-06-23 22:29:23 -0500'>2021-06-23</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=6d388103a4ed8f14f1ac6ac7a2ff22c5fa6b8cd4'>gnu: Add Sollya.</a></td><td>Eric Bavier</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/packages/algebra.scm (sollya): New variable.
* .mailmap: Adjust "proper email" for `git commit`.


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<tr class='logheader'><td><span title='2021-04-21 18:02:27 -0400'>2021-04-21</span></td><td class='logsubject'><a href='/guix/commit/.mailmap?id=449844474da86b5f10a4c5e4f1744e1e3a716d6e'>Update email address for Kei.</a></td><td>Kei Kebreau</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* .mailmap: Remove obsolete email for Kei.


</td></tr>