Jan Engelhardt 0e06fe8148 m4: resolve autoconf-2.68 warnings
Newer autoconf desires proper full quoting and use of AC_LANG_SOURCE.
Import new m4 file from git://dev.medozas.de/m4_jengelh.

m4/gcc4_visibility.m4:4: CHECK_GCC_FVISIBILITY is expanded from...
configure.ac:15: the top level
configure.ac:15: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call
detected in body
2011-12-17 04:17:51 +01:00
..