Don't use a nested function when testing for visibility attribute support.

Don't use a nested function when testing for visibility attribute support.

Some compilers support __attribute__((visibility)), but not nested
functions (e.g. http://www.cprover.org/goto-cc/)

Change-Id: I01a5dd6f5f913664621c4090e2dca177527436bb
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=749983
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=749985
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=749986
Signed-Off-By: Jelmer Vernooij <jelmer@debian.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Mon Nov 10 08:29:19 CET 2014 on sn-devel-104