Revert part of r206963

Specifically the part where we removed a warning to be compatible with GCC, which has been widely regarded as a bad idea.

I'm not quite happy with how obtuse this warning is, especially in the fairly common case of a 32-bit integer literal, so I've got another patch awaiting review that adds a fixit to reduce confusion.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213935 91177308-0d34-0410-b5e6-96231b3b80d8