* flow.c (flow_delete_insn, make_edge, remove_edge): Export.
        * basic-block.h: Declare them.
        * emit-rtl.h (active_insn_p): New.
        (next_active_insn, prev_active_insn): Use it.
        * rtl.h: Declare it.
        * function.c (emit_return_into_block): New.
        (thread_prologue_and_epilogue_insns): Insert return insns instead
        of epilogues when possible.
        * jump.c (jump_optimize_1): Remove code to insert a return insn
        on the fallthru to the exit block.

From-SVN: r31826