Add -fprofile-sample-use to Clang's driver.

This adds a new option -fprofile-sample-use=filename to Clang. It
tells the driver to schedule the SampleProfileLoader pass and passes
on the name of the profile file to use.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194567 91177308-0d34-0410-b5e6-96231b3b80d8
Add an optional mapping from source paths to source contents.

This allows compilation database implementations for distributed build
systems to hand all data to the client to make parsing independent of
the file system.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194571 91177308-0d34-0410-b5e6-96231b3b80d8
Correctly mark first token in the presence of UTF-8 BOM.

Summary: Fixes http://llvm.org/PR17753

Reviewers: klimek

Reviewed By: klimek

CC: cfe-commits, klimek

Differential Revision: http://llvm-reviews.chandlerc.com/D2159

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194576 91177308-0d34-0410-b5e6-96231b3b80d8