-Rename -Wargument-larger-than -> -Wlarge-by-value-copy
-Improve the diagnostic message
-Add some comments

Suggestions by Chris.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@119594 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed