Properly identify 'this' as range-based for container
    
The Loop-Convert transform was mistransforming loops using 'this' implicitly.
Fixed and added tests.

Fixes PR15411.


git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@176436 91177308-0d34-0410-b5e6-96231b3b80d8
Adding failing LoopConvert testcase
    
LoopConvert isn't properly handling iterators whose dereference operator
returns by value. This test case demonstrates the failure.

See PR15437.


git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@176437 91177308-0d34-0410-b5e6-96231b3b80d8