* configure.in, configure: Recognize rs6000-*-aix4*.
* config/powerpc/xm-aix.h: Reduce to include "xm-aix4.h".
* config/rs6000/aix4.mh (XM_FILE): Point to xm-aix4.h.
* config/rs6000/xm-aix4.h: New file.
* config/xm-aix4.h: New file.
From the Mentor work...enable configure & build on rs6000-ibm-aix4.1.*.
Note this is an unbelievably buggy debugger on this host.