Propagate source font modification time to svg during conversion.  Similar to
what upstream commit 95a470e941d9a20fbdaca51334e8b6b9d93cfae4 did for TTF
files.

Submitted upstream at http://github.com/fontforge/fontforge/pull/2696

--- a/fontforge/svg.c
+++ b/fontforge/svg.c
@@ -27,7 +27,6 @@
 #include "fontforgevw.h"
 #include <unistd.h>
 #include <math.h>
-#include <time.h>
 #include <locale.h>
 #include <utype.h>
 #include <chardata.h>
@@ -62,7 +61,6 @@ static int svg_outfontheader(FILE *file, SplineFont *sf,int layer) {
     BlueData bd;
     char *hash, *hasv, ch;
     int minu, maxu, i;
-    time_t now;
     const char *author = GetAuthor();
 
     memset(&info,0,sizeof(info));
@@ -78,9 +76,8 @@ static int svg_outfontheader(FILE *file, SplineFont *sf,int layer) {
 	fprintf( file, "\n-->\n" );
     }
     fprintf( file, "<svg xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" version=\"1.1\">\n" );
-    time(&now);
     fprintf( file, "<metadata>\nCreated by FontForge %d at %s",
-	    FONTFORGE_VERSIONDATE_RAW, ctime(&now) );
+	    FONTFORGE_VERSIONDATE_RAW, ctime((time_t*)&sf->modificationtime) );
     if ( author!=NULL )
 	fprintf(file," By %s\n", author);
     else
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<tr><td><span title='2019-12-08 00:47:26 +0100'>2019-12-08</span></td><td><a href='/guix/commit/gnu/machine?id=a1d7920861a8d6c6774149eaf939eb2636942090'>machine: Remove unnecessary record self-referencing bindings.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-12-07 00:29:10 +0100'>2019-12-07</span></td><td><a href='/guix/commit/gnu/machine?id=2617d956d8ae122128a1ba2cc74983cbd683b042'>machine: ssh: Deprecate missing 'host-key' field.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-12-04 18:16:08 +0100'>2019-12-04</span></td><td><a href='/guix/commit/gnu/machine?id=ed15dfcf31ec35c58f5a44d1d8adf5048da67ea6'>machine: ssh: &lt;machine-ssh-configuration&gt; can include the host key.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-10-22 18:32:52 +0200'>2019-10-22</span></td><td><a href='/guix/commit/gnu/machine?id=c93994b5e43acc6048b81836d30632e015306c92'>machine: digital-ocean: Rename 'enable-ipv6' to 'enable-ipv6?'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-10-22 18:32:52 +0200'>2019-10-22</span></td><td><a href='/guix/commit/gnu/machine?id=12712817ae97eb6305deeaad68ce17c9fa212917'>machine: Implement 'digital-ocean-environment-type'.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-08-17 20:45:13 +0800'>2019-08-17</span></td><td><a href='/guix/commit/gnu/machine?id=02460db0474ff5ac0d867ed6d5b192c062af0abc'>machine: ssh: Fix sanity checks.</a><span class='msg-avail'>...</span></td><td>宋文武</td></tr>
<tr><td><span title='2019-08-16 08:47:28 -0400'>2019-08-16</span></td><td><a href='/guix/commit/gnu/machine?id=4cc5e5204b503afb4536a1e93e2fd7a9f57f12bf'>machine: Use 'become-command'.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-08-15 07:43:13 -0400'>2019-08-15</span></td><td><a href='/guix/commit/gnu/machine?id=3033d59ac9a747b42a1fa6ca6664d4fbc62ca117'>machine: Automatically authorize the coordinator's signing key.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-08-15 07:43:09 -0400'>2019-08-15</span></td><td><a href='/guix/commit/gnu/machine?id=9c70c460a05b2bc60f3f3602f0a2dba0f79ce86c'>machine: Implement 'roll-back-machine'.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
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<tr><td><span title='2019-08-14 15:38:09 -0400'>2019-08-14</span></td><td><a href='/guix/commit/gnu/machine?id=2c8e04f13670c8c7ad8c7195c305960dd1905363'>remote: Build derivations appropriate for the remote's</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-08-07 18:29:07 -0400'>2019-08-07</span></td><td><a href='/guix/commit/gnu/machine?id=d84e9b75b2aba98583531f2876d9298871389585'>machine: Add 'build-locally?' field for managed hosts.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-08-06 16:40:25 -0400'>2019-08-06</span></td><td><a href='/guix/commit/gnu/machine?id=fd3119db4fed02a1f3491460be776a3b5d2b2cd3'>machine: Implement safety checks.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-08-06 15:48:51 -0400'>2019-08-06</span></td><td><a href='/guix/commit/gnu/machine?id=d97ce20400b5d2967bfbc0e9fbfb99bbb2daed4f'>machine: Rename 'system' field.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-07-26 19:19:49 +0200'>2019-07-26</span></td><td><a href='/guix/commit/gnu/machine?id=5c793753b31b1dcd9a554bce953124f7ae88ca9a'>guix system: Add 'reconfigure' module.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-07-18 12:57:00 +0200'>2019-07-18</span></td><td><a href='/guix/commit/gnu/machine?id=53f21b3fe9ed57f0feef003185b561efc9b3e30c'>machine: Fix typo.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-07-06 02:10:04 -0400'>2019-07-06</span></td><td><a href='/guix/commit/gnu/machine?id=fa9edf09e992db7510c7471486dffc93e1e707e5'>gnu: Add machine type for deployment specifications.</a><span class='msg-avail'>...</span></td><td>Jakob L. Kreuze</td></tr>