Add compatibility with glibc 2.32

Created by: ghost

/home/dan/xray-16/src/xrCore/FS_internal.h: In member function ‘virtual void CFileWriter::w(const void*, size_t)’:
/home/dan/xray-16/src/xrCore/FS_internal.h:81:86: error: ‘_sys_errlist’ was not declared in this scope
   81 |                 R_ASSERT3(W == 1, "Can't write mem block to file. Disk maybe full.", _sys_errlist[errno]);
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User side fix was provided at https://github.com/OpenXRay/xray-16/issues/667#issuecomment-700309392

However it would be nice to have it fixed in project codebase instead

From glibc 2.32 announce https://sourceware.org/pipermail/libc-announce/2020/000029.html

* The deprecated symbols sys_errlist, _sys_errlist, sys_nerr, and _sys_nerr
  are no longer available to newly linked binaries, and their declarations
  have been removed from from <stdio.h>.  They are exported solely as
  compatibility symbols to support old binaries.  All programs should use
  strerror or strerror_r instead.