Issue warning when case value is too large to fit

in case condition type. // rdar://11577384.
Test is conditionalized on x86_64-apple triple as
I am not sure if the INT_MAX/LONG_MAX values in the test
will pass this test for other hosts.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172016 91177308-0d34-0410-b5e6-96231b3b80d8