[DEBUGINFO] Add option that allows to disable emission of flags in .loc directives.

Summary:
Some targets do not support extended format of .loc directive and
support only simple format: .loc <FileID> <Line> <Column>. Patch adds
MCAsmInfo flag and option that allows emit .loc directive without
additional flags.

Reviewers: echristo

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45184

llvm-svn: 329089