Summary:
This change turns SanitizerArgs into high-level options
stored in the Driver, which are parsed lazily. This fixes an issue of multiple copies of the same diagnostic message produced by sanitizer arguments parser.

Reviewers: rsmith

Reviewed By: rsmith

CC: chandlerc, eugenis, cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1341

llvm-svn: 188660

Also add some documentation.

Differential Revision: http://llvm-reviews.chandlerc.com/D1346

llvm-svn: 188403

llvm-svn: 188068

llvm-svn: 188058

llvm-svn: 187977

llvm-svn: 187972