Front-end: Fix issue #146: which versions allow double in/out.

Test/400.vert

@@ -0,0 +1,9 @@
+#version 400 core
+
+in double d;   // ERROR, no doubles
+in dvec3 d3;   // ERROR, no doubles
+in dmat4 dm4;  // ERROR, no doubles
+
+void main()
+{
+}