Add keyboard Push-to-talk

Add a Push-To-Talk feature into VI and VI_Settings, plus needed GUI, with a keyboard hook.
Push-to-talk come with 3 modes : 'PressOnce', 'Hold' and 'Off'.
Prevents any recognized VI_phrase trigger to run. Unrecognized things pass anyway.
PTT key can be customised in settings menu.
Default key is 'Scroll', because why not. Default mode is 'Off'.

Maybe it needs modifiers, for "Ctrl+Key"-like macros. And mouse keys support.

For whatever reasons, the keyboard hook doesn't seem to work without "Prefer32Bit" VisualStudio project setting set to "false".
I'm not sure of the implication. Does it mean the program can't run on a 32-bit Windows anymore ?