Add jstopinfo support to llgs

Summary:
This adds support for jstopinfo field of stop-reply packets. This field enables us to avoid
querying full thread stop data on most stops  (see r242593 for more details).

Reviewers: ovyalov, clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D11415

llvm-svn: 242997