- Remove references to `ISTEXTINPUT` as any keyboard event with it's
utf8_buf set can be handled as text input.
- Update references to the key repeat flag.
Moves all `interface_region*` files to C++ except for the tooptip region
which is slightly more complicated. Also move a few other files as well.
This helps to simplify and speed up code, especially through the use
of better C++ data structures. This change builds on all platforms on
the buildbot.
