[ms-inline asm] Test case for r178566.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@178568 91177308-0d34-0410-b5e6-96231b3b80d8
Update assertion string to new name of ArithAssignBinaryOperator

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@178572 91177308-0d34-0410-b5e6-96231b3b80d8