All pointer<->integer conversion truncation warnings I'm aware of are
now enabled for MSVC, to hopefully finally get that tool code 64bit-clean.
I had to adjust the idCVar code for this - it should've been safe enough
(highly unlikely that a valid pointer is exactly 0xFFFFFFFF on 64bit),
but triggered those warnings - now it should behave the same as before
but the warnings (which are now errors) are silenced.