[PATCH] enable default_cxa_atexit for AIX 6.1 and AIX 7.1

[David Edelsohn]

cxa_atexit functionality for AIX was added to libgcc a while ago.  It
seems stable in all of the testing.  This patch enables it by default.

Bootstrapped on powerpc-ibm-aix7.1.0.0, powerpc-ibm-aix7.1.2.0,
powerpc-ibm-aix7.1.3.0

Thanks, David

* config.gcc (powerpc-ibm-aix[6789])[default_use_cxa_atexit]: Set to yes.

Index: config.gcc
===================================================================
--- config.gcc  (revision 229275)
+++ config.gcc  (working copy)
@@ -2540,6 +2540,7 @@
        thread_file='aix'
        use_gcc_stdint=wrap
        extra_headers=altivec.h
+       default_use_cxa_atexit=yes
        ;;
 rs6000-ibm-aix[789].* | powerpc-ibm-aix[789].*)
        tm_file="${tm_file} rs6000/aix.h rs6000/aix71.h rs6000/xcoff.h
rs6000/aix-stdint.h"
@@ -2549,6 +2550,7 @@
        thread_file='aix'
        use_gcc_stdint=wrap
        extra_headers=altivec.h
+       default_use_cxa_atexit=yes
        ;;
 rl78-*-elf*)
        tm_file="dbxelf.h elfos.h newlib-stdint.h ${tm_file}"