Avoid #warning directives on non-GCC compilers. (bug 7683)

Detect GCC and use #warning only on GCC systems.

configure.in

@@ -78,14 +78,16 @@ fi
 AM_CONDITIONAL(MS_LIB_AVAILABLE, test x$ms_librarian = xyes)
 
 WARN_CFLAGS=""
-
 if test "x$GCC" = "xyes"; then
 	WARN_CFLAGS="-Wall -Wpointer-arith -Wstrict-prototypes \
 	-Wmissing-prototypes -Wmissing-declarations \
 	-Wnested-externs -fno-strict-aliasing"
+	AC_DEFINE_UNQUOTED(HAVE_WARNING_CPP_DIRECTIVE,1,
+	[Can use #warning in C files])
 fi
 AC_SUBST(WARN_CFLAGS)
 
+
 dnl ==========================================================================
 
 AM_CONDITIONAL(CROSS_COMPILING, test $cross_compiling = yes)

src/fcfreetype.c

@@ -64,6 +64,7 @@
 
 #include "ftglue.h"
 
+#if HAVE_WARNING_CPP_DIRECTIVE
 #if !HAVE_FT_GET_BDF_PROPERTY
 #warning "No FT_Get_BDF_Property: Please install freetype 2.1.4 or later"
 #endif
@@ -71,6 +72,7 @@
 #if !HAVE_FT_GET_PS_FONT_INFO
 #warning "No FT_Get_PS_Font_Info: Please install freetype 2.1.1 or later"
 #endif
+#endif
 
 /*
  * Keep Han languages separated by eliminating languages