`mrb_funcall_id()` is an attractive and easy-to-use function, but it requires more stack space.
This is because the `mrb_funcall_id()` function takes variable-length arguments and also requires copying to a fixed-length array.

If the `mrb_funcall_argv()` function is called directly, stack consumption can be avoided.
However, it requires an array to be defined, making it less usable.

Therefore, the `MRB_FUNCALL()` macro function is introduced to improve usability.
This is for internal implementation at this time, because if the number of arguments is wrong, the error will be hard to understand at compile time.

Currently, only calls with up to 4 arguments are made. For reserve purposes, calls with up to 6 arguments are valid.
Calls with 7 to 13 arguments will output a "function not defined" error at compile time.
For 14 or more arguments, a seemingly inexplicable error is output.

Also, `mrb_static_assert_expand()` has been renamed to `MRB_VA_EXPAND()` and moved to `include/mruby/common.h`.