Improve the printing of ranges when macros are involved.

Improve the printing of ranges when macros are involved.

Trace the ranges through the macro backtrace better.  This allows better
range highlighting through all levels of the macro bracktrace.  Also some
improvements to backtrace printer for omitting different backtraces.

Patch by Zhengkai Wu.

Differential Revision: http://reviews.llvm.org/D12379

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@248454 91177308-0d34-0410-b5e6-96231b3b80d8