Remove the ifdefs for ULTRIX_STDIO_BOTCH

Not only has Ultrix been long out of support, this ifdef was
working around a bug particular to Ultrix 1.2.
Removed the ifdef for FPUTS_BOTCH

This enabled a workaround for fputs on SunOS 4.0.1 and 4.0.2,
SunOS 4.1.x and later do not have the problem.
Removed the define for ISHISH

Each platform defined their own name in ISHISH. However, nothing
used it, and the list of platforms was severely lacking.
Removed the hints for A/UX and related defines
Removed the hints file for Interactive Unix and related defines

Well, related, singular. It removes BOGUS_GETNAME_RETURN from pp_sys.c
Removed the ifdef & define for VDf

This remained only for compatibility with CPAN, but nothing there
uses it.
Removed the ifdefs for __SC__ in toke.c
Removed the ifdefs for INCOMPLETE_TAINTS

This was added in 5.5/5.6 as a backwards-compatibility measure
when taint was extended to happen in more places.
cpan/IPC-SysV/SysV.xs: Remove the ifdef for INCOMPLETE_TAINTS
cpan/Win32/Win32.xs: Remove the ifdef for INCOMPLETE_TAINTS
Removed OP_IN_REGISTER and related defines.

Added as an experiment in 462e5cf6, it never quite worked, and
recently wasn't even using registers.
perl.h: Always unconditionally include sys/types.h
Replaced an ifdef for sv_dup with USE_ITHREADS
Removed the ifdefs for BUGGY_MSC and BUGGY_MSC6

These are leftovers from the perl 4 era config.h.
Removed DUMP_FDS and dump_fds()

If perl was compiled with -DDUMP_FDS, it would define dump_fds
and add it to the API, although even then nothing used it.
dump_fds() itself was buggy, only checking for fds 0 through 32.
Replaced the last use of HAS_GNULIBC with __GLIBC__
Removed the use of SPARC64_GCC_WORKAROUND

As the name implies, this worked around a bug in gcc, particularly,
gcc 2.x, in SPARC64.  No longer relevant.
fixup, manifest aux
fixup, manifest isc
Removed HAS_SOCKET__bad_code_maybe