Produce a diagnostic if alignas is applied to an expression. Neither C11 nor
C++11 allows that.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173789 91177308-0d34-0410-b5e6-96231b3b80d8
Test update missed in r173789.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173790 91177308-0d34-0410-b5e6-96231b3b80d8