ADT: Remove external uses of ilist_iterator, NFC
Delete the dead code for Write(ilist_iterator) in the IR Verifier,
inline report(ilist_iterator) at its call sites in the MachineVerifier,
and use simple_ilist<>::iterator in SymbolTableListTraits.
The only remaining reference to ilist_iterator outside of the ilist
implementation is from MachineInstrBundleIterator. I'll get rid of that
in a follow-up.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280565
91177308-0d34-0410-b5e6-
96231b3b80d8