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.
Removed HAS_SOCKET__bad_code_maybe
Removed an ifdef for IS_UTF8_CHAR in utf8.c

IS_UTF8_CHAR is defined by utf8.h, so this is always defined.
In fact, later in utf8.c we use it again, this time without the
ifdef.