mesa: Add -fno-trapping-math to CFLAGS.

Cuts about 1k of .text size.

   text    data     bss     dec     hex filename
4983676  197808   26328 5207812  4f7704 i965_dri.so before
4982522  197800   26328 5206650  4f727a i965_dri.so after

Reviewed-by: Roland Scheidegger <sroland@vmware.com>

configure.ac

@@ -286,8 +286,8 @@ if test "x$GCC" = xyes; then
     # Work around aliasing bugs - developers should comment this out
     CFLAGS="$CFLAGS -fno-strict-aliasing"
 
-    # We don't want floating-point math functions to set errno
-    CFLAGS="$CFLAGS -fno-math-errno"
+    # We don't want floating-point math functions to set errno or trap
+    CFLAGS="$CFLAGS -fno-math-errno -fno-trapping-math"
 
     # gcc's builtin memcmp is slower than glibc's
     # http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43052