This is the second of three patches to implement support for the .loc directive

This is the second of three patches to implement support for the .loc directive
and output the dwarf line number tables.  This takes the current loc info after
an instruction is assembled and saves the needed info into an object that has
vector and for each section.  These objects will be used for the final patch to
build and emit the encoded dwarf line number tables.  Again for now this is only
in the Mach-O streamer but at some point will move to a more generic place.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112668 91177308-0d34-0410-b5e6-96231b3b80d8