Drop -Wstrict-prototypes for GD

Author: Girgias

ext/gd/config.m4

@@ -149,6 +149,9 @@ if test "$PHP_GD" != "no"; then
                   libgd/gd_transform.c libgd/gd_crop.c libgd/gd_interpolation.c libgd/gd_matrix.c \
                   libgd/gd_bmp.c libgd/gd_tga.c"
 
+dnl Disable strict prototypes as GD takes advantages of variadic function signatures for function pointers.
+    AX_CHECK_COMPILE_FLAG([-Wno-strict-prototypes], GC_CFLAGS="$GD_CFLAGS -Wnostrict-prototypes", , [-Werror])
+
 dnl check for fabsf and floorf which are available since C99
     AC_CHECK_FUNCS(fabsf floorf)