Debug Info: update interface for CreateEnumType and getOrCreateRecordFwdDecl.

Both functions will take a Type pointer instead of a Decl pointer. This helps
with follow-up type uniquing patches, which need the Type pointer to call
CXX mangler to generate unique identifiers.

No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189519 91177308-0d34-0410-b5e6-96231b3b80d8