Add new evaluate* functions
Add new evaluate* functions

These functions are added in order to improve how chisel evaluates user input,
and how chisel evaluates objc. User input needs to be evaluated using whatever
language is currently active, and chisel needs to be evaluated in objc. In
addition, these functions will pave the way to removing eobjc, pobjc, etc.

dopcn/chisel,zats/chisel,dopcn/chisel,facebook/chisel,facebook/chisel,facebook/chisel,dopcn/chisel