[codeview] Add IntroducingVirtual debug info flag

CodeView needs to know if a virtual method was introduced in the current
class, and base classes may not have complete type information, so we
need to thread this bit through from the frontend.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273453 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed