Refactor constant expression handling and make a couple of tweaks to make it a
bit more robust against future changes. This includes a slight diagnostic
improvement: if we know we're only trying to form a constant expression, take
the first diagnostic which shows the expression is not a constant expression,
rather than preferring the first one which makes the expression unfoldable.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194098 91177308-0d34-0410-b5e6-96231b3b80d8
Simplify: we don't care why constant evaluation might have failed when we're
checking an expression for constant overflow.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194099 91177308-0d34-0410-b5e6-96231b3b80d8
ObjectiveC migrator. Please annotation of properties with 
NS_RETURNS_INNER_POINTER under -objcmt-returns-innerpointer-property
flag (off by default), as older compilers do not support such annotations.
// rdar://15396636


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194100 91177308-0d34-0410-b5e6-96231b3b80d8