Switch Sema::UnusedFileScopedDecls over to a LazyVector. 
  - Added LazyVector::erase() to support this use case.
  - Factored out the LazyDecl-of-Decls to RecordData translation in
  the ASTWriter. There is still a pile of code duplication here to
  eliminate.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@136270 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed