Fix non-only or named "void" in parameter lists

'void' must be the only parameter and unnamed to indicate no parameters.
Previously, the check for functions with first parameter of void
pointer, etc. didn't consider the illegal forms, so those could pass
compilation.

Author: lumynou5

src/parser.c

@@ -735,7 +735,11 @@ void read_parameter_list_decl(func_t *func, int anon)
         if (lex_accept(T_close_bracket))
             return;
         func->param_defs[vn].type = TY_void;
-        read_inner_var_decl(&func->param_defs[vn++], anon, 1);
+        read_inner_var_decl(&func->param_defs[vn], anon, 1);
+        if (!func->param_defs[vn].is_ptr && !func->param_defs[vn].is_func &&
+            !func->param_defs[vn].array_size)
+            error("'void' must be the only parameter and unnamed");
+        vn++;
         lex_accept(T_comma);
     }