Add a new method call operator, and more.

The '.' operator now represents method calls. A function f: (a, b)->c
can be called as a.f(b), which is equivalent to f(a, b). Besides
this change, all reserved operators now have a negative precedence
(it's relative, remember?), and some function names were changed.

src/interactive.c

@@ -198,7 +198,7 @@ libab_result loop(libab* ab, int interaction_count, libab_ref* scope) {
         if (eval_result != LIBAB_SUCCESS) {
             printf("Invalid input (error code %d).\n", eval_result);
         } else {
-            result = libab_run_function_scoped(ab, "print", scope, &call_into, 1, &eval_into);
+            result = libab_call_function_scoped(ab, "print", scope, &call_into, 1, &eval_into);
             if(result == LIBAB_BAD_CALL) {
                 printf("(?)\n");
                 result = LIBAB_SUCCESS;