Add VDA m4

m4/vda.m4

@@ -0,0 +1,13 @@
+AC_DEFUN([MOONLIGHT_CHECK_VDA],
+[
+	AC_ARG_WITH(vda, AC_HELP_STRING([--with-vda=yes|no],
+		[If you want to enable support for vda]),
+		[], [with_vda=no])
+
+	if test x$with_vda = xyes; then
+		LDFLAGS="$LDFLAGS -framework VideoDecodeAcceleration"
+    	AC_DEFINE([INCLUDE_VDA], [1], [Include support for vda])
+	fi
+
+	AM_CONDITIONAL(INCLUDE_VDA, test x$with_vda = xyes)
+])