Add two new APIs for active keyboard layout.

This goes with https://github.com/adobe/brackets/pull/9652.
Also, this is very poorly documented but it seems like this is the value here is just the numerical load order of the keyboard layout with its local. So 0x0409 is US English, 0x10409 is US English with a Dvorak layout, etc... There doesn't seem to be any concrete data that says 0x10409 will always be Dvorak.  Futhermore, there could be additional layouts that are added to this (although this has no impact to Brackets) 

I'm just not certain that this will be consistent across all versions, distributions of Windows.