vector [Sema]. Check for proper use of 's' char prefix
(which indicates vector expression is a string of hex
values) instead of crashing in code gen. // rdar://16492792


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@205557 91177308-0d34-0410-b5e6-96231b3b80d8