Stop printing macro backtraces that don't help diagnostics.

Stop printing macro backtraces that don't help diagnostics.

When displaying the macro backtrace, ignore some of the backtraces that do not
provide extra information to the diagnostic.  Typically, if the problem is
entirely contained within a macro argument, the macro expansion is often not
needed.  Also take into account SourceRange's attached to the diagnostic when
selecting which backtraces to ignore.  Two previous test cases have also been
updated.

Patch by Zhengkai Wu, with minor formatting fixes.

Differential Revision: http://reviews.llvm.org/D11778

llvm-svn: 244788