Remaining host configuration fragments

[DJ Delorie]

> Second, adjusting PATH_SEPARATOR, DIR_SEPARATOR, DIR_SEPARATOR_2, and
> HAVE_DOS_BASED_FILE_SYSTEM.  This is done by i386/xm-cygwin.h,
> i386/xm-djgpp.h, i386/xm-mingw32.h, and i386/xm-vsta.h.  In canonical
> form, all four of these are set as a block.  However, xm-cygwin.h does
> not set PATH_SEPARATOR, and xm-vsta.h only sets PATH_SEPARATOR (why?)
> 
> I think it would be appropriate to slave the SEPARATOR macros to
> HAVE_DOS_BASED_FILE_SYSTEM, and move HDBFS into xm_defines.

Ideally, the src/include/filesystem.h from "over there" should be made
common to gcc, and use that.

Cygwin tries real hard to hide dos-isms, not sure if it would be OK to
have both path separators.

> Well, arguably the irix5 and VAX VMS configurations should be
> scrapped.

Why?  I've still got an irix5 machine myself...