* configure.in: Recognize aix4 specially as some aspects

    * configure.in: Recognize aix4 specially as some aspects
        of aix4 need different handling than aix3.
        * configure: Updated.
        * config/powerpc/{aix4.mh,aix4.mt,tm-ppc-aix4.h}: New files
        specific to aix4 support on the power pc.
        * config/powerpc/tm-ppc-aix.h (DONT_RELOCATE_SYMFILE_OBJFILE): Do
        not defined.  The aix4 specific target files will do that.
        * config/rs6000/{aix4,mh,aix4,mt,tm-rs6000-aix4.h}: New files
        specific to aix4 support on the rs6000.

        * config/rs6000/tm-rs6000.h (CONVERT_FROM_FUNC_PTR_ADDR): Don't
        do the conversion if the pointer is not a magic aix function
        pointer.
        * rs6000-tdep.c: Include objfiles.h and symtab.h.
        (is_magic_function_pointer): New function.

        * rs6000-tdep.c (skip_prologue): Refine check for frameless
        functions.  Handle b .+4 emitted by aix4 compilers.  Only
        allow one load of a minimal toc pointer.  Handle aix4 compiler's
        code for alloca.

        * rs6000-tdep.c (find_toc_address): Report an error if no toc was
        found rather than possibly core dumping.

        * partial-stab.h: Handle extra field generated by the aix4 compiler
        for enumerations.
        * stabsread.c (read_enum_type): Likewise.