Centralize the management of CXXRecordDecl::DefinitionData's

HasTrivialConstructor, HasTrivialCopyConstructor,
HasTrivialCopyAssignment, and HasTrivialDestructor bits in
CXXRecordDecl's methods. This completes all but the Abstract bit and
the set of conversion functions, both of which will require a bit of
extra work. The majority of <rdar://problem/8459981> is now
implemented (but not all of it).

llvm-svn: 114929