Add way to detect keyboard layout

[FredyH]

Currently there is no way to detect someone's keyboard layout. This would be helpful whenever one wants to detect keypresses for keys that might differ depending on the keyboard layout.

[klen-list]

Also this would be a good addition to SetDrawLanguageID

[klen-list]

@robotboy655 can we get https://github.com/ValveSoftware/source-sdk-2013/blob/0d8dceea4310fde5706b3ce1c70609d72a38efdf/sp/src/public/vgui/IInput.h#L95-L98 in https://wiki.facepunch.com/gmod/input library pls?

[garryspins]

literally a 2 second addition that would make a world of difference, this has been a constricting limitation for as long as i can remember, please add this.