[analyzer] LoopUnrolling: update the matched assignment operators

Extended the matched assignment operators when checking for bound changes in a body of the loop by using the freshly added isAssignmentOperator matcher.
This covers all the (current) possible assignments, tests added as well.

Differential Revision: https://reviews.llvm.org/D38921



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@328619 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed