Analysis: Only allow the move-constructor for IVUsers

Force IVUsers to be moved instead of copied, properly update Parent
pointers in IVStrideUse when IVUsers is moved, and make sure we have
move constructors available in iplist and ilist.

I came across this in a WIP patch that deleted the copy constructors
from ilist.  I was surprised to find that IVUsersAnalysis couldn't be
registered in the new pass manager.

It's not clear to me whether IVUsers was getting moved only when empty,
but if it was being moved when it was non-empty then this fixes a
pointer invalidation bug and should give some sort of speedup.  Note
that the bugfix would be necessary even for a copy constructor.

llvm-svn: 281181