Fix segfault with invalid function def

This invalid function definition:
  int f()[] {}
was tried to be handled but there was no testcase if it actually worked.
This fixes it and adds a TCC only testcase.

tccgen.c

@@ -4013,7 +4013,7 @@ static int post_type(CType *type, AttributeDef *ad, int storage, int td)
         if (tok == '[') {
             next();
             skip(']'); /* only handle simple "[]" */
-            type->t |= VT_PTR;
+            mk_pointer(type);
         }
         /* we push a anonymous symbol which will contain the function prototype */
         ad->a.func_args = arg_size;

tests/tcctest.c

@@ -176,6 +176,11 @@ static int onetwothree = 123;
 #define B3 4
 #endif
 
+#ifdef __TINYC__
+/* We try to handle this syntax.  Make at least sure it doesn't segfault.  */
+char invalid_function_def()[] {}
+#endif
+
 #define __INT64_C(c)	c ## LL
 #define INT64_MIN	(-__INT64_C(9223372036854775807)-1)