purge_addressof bootstrap failure (was fix opt/8634)

[David Edelsohn]

The follow-up patch

        * function.c (postponed_insns): New.
        (purge_addressof_1): Postpone processing of insns if addressofs
        are not put into stack.
        (purge_addressof): Process postponed insns.

introduced a bootstrap failure on AIX:

/gcc/dje/build/powerpc-ibm-aix4.3.3.0-20030408/powerpc-ibm-aix4.3.3.0/pthread/libstdc++-v3/include/bits/istream.tcc: In
   function `std::basic_istream<_CharT, _Traits>& 
   std::operator>>(std::basic_istream<_CharT, _Traits>&, 
   std::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char, _Traits = 
   std::char_traits<char>, _Alloc = std::allocator<char>]':
/gcc/dje/src/libstdc++-v3/src/misc-inst.cc:47:   instantiated from here
/gcc/dje/build/powerpc-ibm-aix4.3.3.0-20030408/powerpc-ibm-aix4.3.3.0/pthread/libstdc++-v3/include/bits/istream.tcc:1137: internal compiler error: RTL
   flag check: CONST_OR_PURE_CALL_P used with unexpected rtx code `insn_list' 
   in sched_analyze, at sched-deps.c:1274

David