* GCC documents -fvisibility at least as far back as the GCC 4.0 online
  documentation at
  <https://gcc.gnu.org/onlinedocs/gcc-4.0.4/gcc/Code-Gen-Options.html>.

* For external code, odk/settings/settings.mk unconditionally set
  HAVE_GCC_VISIBILITY_FEATURE for all platforms other than Windows.

Make this a fatal configure error for now.  The check should be removed
completely after LO 5.3 branch-off.

Change-Id: I1de415b6ed1591e0a7b6640ece861b6f0ef74112
Reviewed-on: https://gerrit.libreoffice.org/29073Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Tested-by: Stephan Bergmann <sbergman@redhat.com>