AIX atomicity.h support

[David Edelsohn]

	Would the following patch be acceptable to allow v3 to use an AIX
OS-specific version of atomicity.h instead of an architecture-specific
one?  The CPU_FLAGS hack only covers up the symptom on newer,
PowerPC-based RS/6000 systems, it does not solve the problem: it is
invalid to have PowerPC code in common-mode libraries.

	I sent an AIX implementation of atomicity.h
(config/aix/bits/atomicity.h, not config/powerpc/bits/atomicity.h) last
May.

	Current the config/cpu directories only contain bits/atomicity.h.
I do not know whether it is better to point cpu_include_dir at the os
directory or to point it at some empty directory and let CPP find the file
in config/aix/bits/atomicity.h.

	I am not sure what to do about src/Makefile.am:myinstallheaders
installing $(cpu_headers) either.

David


Index: acinclude.m4
===================================================================
RCS file: /cvs/gcc/egcs/libstdc++-v3/acinclude.m4,v
retrieving revision 1.59
diff -c -p -r1.59 acinclude.m4
*** acinclude.m4	2000/09/12 01:06:02	1.59
--- acinclude.m4	2000/09/25 19:55:57
*************** AC_DEFUN(GLIBCPP_CHECK_CPU, [
*** 714,721 ****
  	cpu_include_dir="config/cpu/i486"
          ;;
        powerpc | rs6000)
! 	cpu_include_dir="config/cpu/powerpc"
!     	CPU_FLAGS='-mcpu=powerpc'
          ;;
        sparc64 | ultrasparc)
  	cpu_include_dir="config/cpu/sparc/sparc64"
--- 714,729 ----
  	cpu_include_dir="config/cpu/i486"
          ;;
        powerpc | rs6000)
! 	case "${target_os}" in
! 	  aix3*)
! 	    cpu_include_dir="config/cpu/generic"
! 	    ;;
! 	  aix[456789]*)
! 	    cpu_include_dir="config/aix"
! 	    ;;
! 	  *)
! 	    cpu_include_dir="config/cpu/powerpc"
! 	    ;;
          ;;
        sparc64 | ultrasparc)
  	cpu_include_dir="config/cpu/sparc/sparc64"