Add rapid fire ctrl interface, minor cleanup.
Properly send the right analog to the game.

I don't think this was actually working before.
Add keymap support for alt/shift/ctrl on Windows.

WM_KEYDOWN only gets VK_SHIFT, not L or R.  We could detect which on
press, but not on release.  It's simpler to just resend both.
Add a rapid fire virtual key, like before.
Make it easier to test the pause button.
Make pause/speed virtual buttons work again.

Fixes #2669.
Remove some unused keyboard code, avoid confusion.
Remove some no longer used xinput stuff.
Merge pull request #2672 from unknownbrackets/ctrl-rapid

Add back rapid fire, make it possible to use on other platforms