Add a hotkey for disabling the framelimit.

Atm this is hardcoded to '\t'.
Add set/get functions for IsFramelimiterTempDisabled
drop Host_GetKeyState

This function isn't used any more and it shouldn't be used at all as it generates a sync request to the x11 server. So it has to wait for a complete round trip time.
Merge pull request #81 from degasus/skip_framelimit_hotkey

Add a hotkey for disabling the framelimit.