[CONCEPTS] Parsing of concept keyword
Summary: This change adds parsing for the concept keyword in a
declaration and tracks the location. Diagnostic testing added for
invalid use of concept keyword.
Reviewers: faisalv, fraggamuffin, rsmith, hubert.reinterpretcast
Reviewed By: rsmith, hubert.reinterpretcast
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D10528
Patch by Nathan Wilson!
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@241060
91177308-0d34-0410-b5e6-
96231b3b80d8