RS/6000 portability changes (for hosting cross-debuggers).

RS/6000 portability changes (for hosting cross-debuggers).

* breakpoint.c (fixup_breakpoints):  Re-kludge to IBM6000_TARGET.
* buildsym.c, rs6000-xdep.c, rs6000-tdep.c, tm-rs6000.h,
xcoffexec.c, xcoffread.c:  Rename aixcoff to xcoff everywhere.
* printcmd.c (print_frame_args):  Remove an RS/6000 dependency.
* stabsread.c (define_symbol):  Remove RS/6000 dependencies.
* tm-rs6000.h (ATTACH_DETACH):  Remove: host-dependent.
(PTRACE_ATTACH, PTRACE_DETACH):  Remove: host-dep.
(NO_SINGLE_STEP):  Add, target-dependent.
(loadinfotextindex):  Lowercase, remove "aix_".
* xm-rs6000.h:  Add <sys/ptrace.h> for infptrace.c.
(NO_SINGLE_STEP):  Remove, target-dependent.
* xcoffexec.c (vmap_symtab):  Cleanup #if 0'd code.
* xcoffread.c:  Only build file if RS/6000 native GDB.
(build_function_symbol):  Remove #if 0'd code.
* rs6000-tdep.c:  Cleanup.  Add static fn protos.
Use CORE_ADDR for addresses throughout.  Make void fns void.
(pop_dummy_frame):  Add FIXME about bogosity of design here.
(rs6000_struct_return_address):  Ditto.
(frameless_function_invocation, frame_get_cache_fsr,
frame_initial_stack_address, xcoff_relocate_symtab,
xcoff_init_loadinfo, free_loadinfo, xcoff_add_toc_to_loadinfo,
add_text_to_loadinfo, find_toc_address):  Move from xdep file.
Use CORE_ADDRs.  Change identifiers to lowercase.

* rs6000-xdep.c:  Make whole file conditional on native RS/6000,
supplying dummy routines if non-native.  Add prototype for
static exec_one_dummy_insn.  Move a mess of functions to
rs6000-tdep.c (as above).  Remove #if 0'd code.

* config/rs6000.mh (XDEPFILES):  Move xcoffexec.o to target side.
(XM_CLIBS):  Add -lm to circumvent AIX 3.2 libc ldexp bug.
* config/rs6000.mt (TDEPFILES):  Adopt xcoffexec.o.