mesa: Use AC_HEADER_MAJOR to include correct header for major().

Gentoo has been smoke testing an upcoming change to glibc.

Bugzilla: https://bugs.gentoo.org/show_bug.cgi?id=580392
diff --git a/configure.ac b/configure.ac
index 5c196a9..f6b27ae 100644
--- a/configure.ac
+++ b/configure.ac
@@ -777,6 +777,7 @@
     esac
 fi
 
+AC_HEADER_MAJOR
 AC_CHECK_HEADER([xlocale.h], [DEFINES="$DEFINES -DHAVE_XLOCALE_H"])
 AC_CHECK_HEADER([sys/sysctl.h], [DEFINES="$DEFINES -DHAVE_SYS_SYSCTL_H"])
 AC_CHECK_FUNC([strtof], [DEFINES="$DEFINES -DHAVE_STRTOF"])