Transform for loops over pseudo-arrays only if begin/end members exist

For loops using pseudo-arrays, classes that can be used like arrays from
the Loop Convert Transform's point of view, should only get transformed
if the pseudo-array class has begin()/end() members for the
range-based for-loop to call.

Free versions of begin()/end() should also be allowed but this is an
enhancement for another revision.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@181539 91177308-0d34-0410-b5e6-96231b3b80d8