Fix double expansion of macro arguments.

This adds a new fullyExpanded flag that makes sure that macro arguments
only get expanded once. This can happen either in PrescanMacroArg, or, if
there is token pasting or a function-like macro name has been passed as
an argument and may need to be expanded when used as a function.

Test/baseResults/preprocessor.function_macro.vert.out

@@ -13,9 +13,12 @@
 
 
 
+
+
 int main(){
   gl_Position = vec4(3 + 1, 3 + 4, 3 + 1);
   gl_Position = vec4(1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12);
   gl_Position = vec4(4 + 3 + 3);
+  gl_Position = 4 + 3 + F . a;
 }