* Move DerivedType::addAbstractTypeUser from DerivedType.h

* Move DerivedType::addAbstractTypeUser from DerivedType.h
* Refactor a bunch of code.  Types now only remove one subelement at a time
  when they are told that they have changed
* Improve debugging output, add more assertions...
* FIX Bugs:
  * test/Regression/Assembler/2002-04-04-PureVirtMethCall.ll
  * test/Regression/Assembler/2002-04-04-PureVirtMethCall2.ll
  * The change to fix these bugs was the to ValTypeBase::refineAbstractType
    method.  Basically we #if 0'd out the chunk of code there and make the
    table get reorganized EVEN IF the type has the same pointer.  Merging
    opportunities were being missed!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2121 91177308-0d34-0410-b5e6-96231b3b80d8