Typedef for a method exposed in the mruby interpreter.
This function signature is used for all types of mruby methods, including instance methods, class methods, singleton methods, and global methods.
slf is the method receiver, e.g.
s in the following invocation of
s = 'artichoke crate' s.start_with?('artichoke')
To extract method arguments, use
mrb_get_args! and the supplied