DIR_SEPARATOR patches

[Mark E.]

These patches deal with the two directory separators that DOS allows. 
The gcc.c change creates a new macro 'IS_DIR_SEPARATOR' to hide 
the nasty details.

If this patch is acceptable, patches for cccp.c and prefix.c dealing with 
the same issue will follow.

Changelog:

* gcc/config/i386/xm-djgpp.h
  (DIR_SEPARATOR): Set to '/'.
  (DIR_SEPARATOR_2): New macro. Set to '\\'.
  (HAVE_DOS_BASED_FILESYSTEM): New macro. Define.

* gcc/gcc.c
  (IS_DIR_SEPARATOR): New macro. Checks whether or not
        a given character is a directory separator.
  (find_a_file): Use it.
  (convert_filename): Likewise.
  (process_command): Likewise.
  (do_spec_1): Likewise.
  (main): Likewise.

BTW Jeff, sorry about the last set of collect2 patches. I should have 
checked everything over more carefully. This time, I had the coding 
standards on the screen for reference as I made my changes.

--- 
Mark Elbrecht, snowball3@usa.net
http://snowball.digitalspace.net/