Don't get confused on the number of braces when braces start after the first __asm

Summary:
Without this, we would not consume the closing brace which would cause
the parser to start consuming C++ and bad things would happen.

Reviewers: majnemer

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4505

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@213032 91177308-0d34-0410-b5e6-96231b3b80d8