Issue diagnostic when constructor or destructor
return void expression. // rdar://15366494
pr17759.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@196296 91177308-0d34-0410-b5e6-96231b3b80d8
clang-format: Improve clang-format's documentation of ColumnLimit=0.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@196297 91177308-0d34-0410-b5e6-96231b3b80d8