cookie argument to the SourceMgr diagnostic stuff. This cleanly separates
LLVMContext's inlineasm handler from the sourcemgr error handling
definition, increasing type safety and cleaning things up.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119486 91177308-0d34-0410-b5e6-96231b3b80d8