* flow.c (proagate_one_insn): Remove useless assignment.
* jump.c (delete_insn): Tidy.
* loop.c (try_copy_prop): When deleting an instruction with a
REG_RETVAL note, delete the entire libcall sequence.
(loop_delete_insns): New function.
* unroll.c (initial_reg_note_copy): Copy INSN_LIST notes, even if
we're not substituting into them yet.