First bit of support for the dwarf .loc directive. This patch updates the

needed parsing for the .loc directive and saves the current info from that
into the context.  The next patch will take the current loc info after an
instruction is assembled and save that info into a vector for each section for
use to build the line number tables.  The patch after that will encode the info
from those vectors into the output file as the dwarf line tables.

llvm-svn: 111956