Provide a 'mach_print' symbol in libc.

--- a/sysdeps/mach/hurd/i386/libc.abilist	2020-04-01 19:22:44.710088821 +0200
+++ b/sysdeps/mach/hurd/i386/libc.abilist	2020-04-01 19:22:52.062051161 +0200
@@ -338,6 +338,7 @@
 GLIBC_2.2.6 __mach_port_allocate F
 GLIBC_2.2.6 __mach_port_deallocate F
 GLIBC_2.2.6 __mach_port_insert_right F
+GLIBC_2.21 __mach_print F
 GLIBC_2.2.6 __mach_reply_port F
 GLIBC_2.2.6 __mach_task_self_ D 0x4
 GLIBC_2.2.6 __mach_thread_self F

--- a/mach/Versions
+++ b/mach/Versions
@@ -56,6 +56,7 @@
   }
   GLIBC_2.21 {
     __mach_host_self_;
+    mach_print;
   }
 
   HURD_CTHREADS_0.3 {
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<tr><td><span title='2022-09-13 00:20:35 -0400'>2022-09-13</span></td><td><a href='/guix/commit/gnu/packages/patches/gdm-elogind-support.patch?id=97313b9b0c5d5977e66f318345523f5a2f3117e5'>gnu: gdm: Update to 42.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/gnome.scm (gdm): Update to 42.0.
[inputs]: Add libgudev.
* gnu/packages/patches/gdm-default-session.patch: Rebase patch.
* gnu/packages/patches/gdm-elogind-support.patch: Likewise.
* gnu/packages/patches/gdm-pass-gdk-pixbuf-loader-env.patch: Likewise.
* gnu/packages/patches/gdm-remove-hardcoded-xwayland-path.patch: Likewise.
* gnu/packages/patches/gdm-wayland-session-wrapper-from-env.patch: Likewise.
</span></span></td><td>Maxim Cournoyer</td></tr>