PATCH/Ada: Fix DIR_SEPARATOR bug on win32 targets

[Arnaud Charlet]

> I think the problem is that Ada also needs its own version of IS_DIRECTORY_SEPARATOR.
> The problem with generating the support file was with gnatchop.  This
> quick hack fixes that problem:

I don't see how your patch fixes anything, since the line below the one you've
modified already references Directory_Separator which should be '\'

Actually if you need this patch, it most likely means that your patch
broke gnatchop and other tools, and that GNAT.OS_Lib.Directory_Separator
is no longer '\'

As for the gnatmake failure, it could also be related to your change.

In other words, not OK for your patch until these errors are understood.

Arno