Add a new "NewDebugLoc" class which will eventually replace DebugLoc,

and will replace the 'DbgInfo' member in Instruction.

The benefit of NewDebugLoc is that it is compact (8 bytes vs 12/24 
bytes for the DbgInfo member in Instruction on a 32/64 bit system),
it means that we will end up not having to allocate MDNodes to 
represent the "DILocations" in common cases of -O0 -g, and it is
much more efficient to get things out of than the MDNode.

llvm-svn: 100072