DOS/Windows-specific code: all the rest

[Eli Zaretskii <eliz@is.elta.co.il>]

Finally, there were several additional Grep hits, for which I'm unsure
what to do:

  - Some files config/*/*cygwin.h want to be backward compatible to
    old Cygwin versions and use __CYGWIN32__ for that.

  - Many files in rdi-share/ use COMPILING_ON_WINDOWS and
    __CYGWIN32__, partly for backward compatibility.  rdi-share/host.h
    also uses _MSC_VER.

Chris, could you comment on these?

  - There's some sporadic (and probably obsolete by now) support for
    GO32 and Windows in remote-array.c, remote-e7000.c, and
    ser-e7kpc.c.  The latter two seem to use DOS/Windows as their only
    host systems, so perhaps it's okay to leave the #ifdef's alone.

  - ser-ocd.c is Windows- and wiggler-specific.  If someone is going
    to make it less proprietary (see the recent discussion Re: gpl,
    gdb and wigglers.dll), then we should revisit this file after it
    is changed; if not, I'd suggest to leave it alone for now.

  - What's the story with files 29k-share/udi/ ?  udi2go32.c seems to
    be DJGPP-specific, while udi2soc.c and udr.c are the other way
    around: all their code is ifdef'ed away under DJGPP.

  - m32r-rom.c uses _MSC_VER to ifdef away a bunch of functions,
    header files, and commands.  Does anyone know which compiler needs
    that, and why?  (I mean, Windows _does_ support networking,
    right?)

  - nindy-share/ttyflush.c uses _MSC_VER to use _sleep instead of
    sleep.  Again, for which compiler is this needed?

  - should we bother about utils/amd-udi/udi/* files?  Two of them use
    _MSC_VER.