Change uses of:

  Type::getAsReferenceType() -> Type::getAs<ReferenceType>()
  Type::getAsRecordType() -> Type::getAs<RecordType>()
  Type::getAsPointerType() -> Type::getAs<PointerType>()
  Type::getAsBlockPointerType() -> Type::getAs<BlockPointerType>()
  Type::getAsLValueReferenceType() -> Type::getAs<LValueReferenceType>()
  Type::getAsRValueReferenceType() -> Type::getAs<RValueReferenceType>()
  Type::getAsMemberPointerType() -> Type::getAs<MemberPointerType>()
  Type::getAsReferenceType() -> Type::getAs<ReferenceType>()
  Type::getAsTagType() -> Type::getAs<TagType>()
  
And remove Type::getAsReferenceType(), etc.

This change is similar to one I made a couple weeks ago, but that was partly
reverted pending some additional design discussion. With Doug's pending smart
pointer changes for Types, it seemed natural to take this approach.

llvm-svn: 77510