Support: Stop using iplist in Recycler

Recycler just needs a singly-linked list, and it takes less (and
simpler) code to hand-roll one of those than to build up the equivalent
`iplist_traits`.  In theory, this should speed things up a bit too, but
this is really just a drive-by cleanup so I haven't measured.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249615 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed