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

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100072 91177308-0d34-0410-b5e6-96231b3b80d8