Use DiagnosticInfo facility.

Summary:
The sample profiler pass emits several error messages. Instead of
just aborting the compiler with report_fatal_error, we can emit
better messages using DiagnosticInfo.

This adds a new sub-class of DiagnosticInfo to handle the sample
profiler.

Reviewers: chandlerc, qcolombet

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D3086

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203976 91177308-0d34-0410-b5e6-96231b3b80d8
Re-format SampleProfile.cpp with clang-format. No functional changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203977 91177308-0d34-0410-b5e6-96231b3b80d8
MC: don't create a backtrace for diagnostics.

For better or worse, this is currently the normal error reporting path
when dealing with backend errors from inline assembly. It's not just
internal compiler issues that come through here, so we shouldn't be
creating a backtrace on this path.

rdar://16329947

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203979 91177308-0d34-0410-b5e6-96231b3b80d8