Fix bug (and add test) for a function-like-macro appearing as a non-macro.

That is, when a function-like macro appears in the content without
parentheses it should be accepted and passed on through, (previously
the parser was regarding this as a syntax error).

glcpp-parse.y

@@ -133,6 +133,10 @@ content:
 		printf ("%s", $1);
 		talloc_free ($1);
 	}
+|	FUNC_MACRO {
+		printf ("%s", $1);
+		talloc_free ($1);
+	}
 |	macro {
 		_print_string_list ($1);
 	}

tests/025-func-macro-as-non-macro.c

@@ -0,0 +1,2 @@
+#define foo(bar) bar
+foo