Constify most methods. We could have constified doInitialization and

doFinalization too except that would have made them shadow, not override,
the parent class :-P.

Allow *any* constant cast expression between pointers and longs,
or vice-versa, or any widening (not just same-size) conversion that
isLosslesslyConvertibleTo approves. This fixes oopack.

llvm-svn: 7288