[RS4GC] Use "deopt" operand bundles
This is a step towards using operand bundles to carry deopt state till
RewriteStatepointsForGC. The change adds a flag to
RewriteStatepointsForGC that teaches it to pick up deopt state from a
"deopt" operand bundle attached to the call or invoke it is
The command line flag added, -rs4gc-use-deopt-bundles, will only exist
for a short while. Once we are able to pipe deopt bundle state through
the full optimization pipeline without problems, we will "constant fold"
-rs4gc-use-deopt-bundles to true.
Reviewers: swaroop.sridhar, reames
Subscribers: llvm-commits, sanjoy
Differential Revision: http://reviews.llvm.org/D13372