DI: Remove DIDerivedTypeBase

Remove an unnecessary (and confusing) common subclass for
`DIDerivedType` and `DICompositeType`.  These classes aren't really
related, and even in the old debug info hierarchy, there was a
long-standing FIXME to separate them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243152 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed