Problem: We have `P_(BOOL|NUM|STRING)` macros to represent an option's type, which is redundant because `OptValType` can already do that. The current implementation of option type flags is also too limited to allow adding multitype options in the future.
Solution: Remove `P_(BOOL|NUM|STRING)` and replace it with a new `type_flags` attribute in `vimoption_T`. Also do some groundwork for adding multitype options in the future.
Side-effects: Attempting to set an invalid keycode option (e.g. `set t_foo=123`) no longer gives an error.
3c2c022e5e
