The zlib link probe compiles a program that calls memset() with only <zlib.h>
included. Since GCC 14 an implicit function declaration is an error, so the
probe fails on every current toolchain, HAVE_ZLIB is left undefined and
mcstruct loses the inflate support it is meant to gate -- silently, because
the check is a bare AC_CHECK_HEADERS with no --enable switch to report on and
nothing in configure's summary mentions zlib.

Both the generated configure and configure.ac are patched: the tarball is
bootstrapped and we do not autoreconf, but leaving configure.ac wrong would
undo the fix for anyone who does.

Not reported upstream yet.

--- a/configure
+++ b/configure
@@ -27189,6 +27189,7 @@
 printf %s "checking for inflateInit_ in -lz... " >&6; }
     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
+#include <string.h>
 #include <zlib.h>
 int
 main (void)
--- a/configure.ac
+++ b/configure.ac
@@ -612,7 +612,8 @@
     mc_saved_LIBS="$LIBS"
     LIBS="$LIBS -lz"
     AC_MSG_CHECKING([for inflateInit_ in -lz])
-    AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <zlib.h>]],
+    AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <string.h>
+#include <zlib.h>]],
                                     [[z_stream z; memset (&z, 0, sizeof (z));
                                       inflateInit (&z); inflateEnd (&z);]])],
         [AC_MSG_RESULT([yes])