mount functionality

[Robert Collins]

I notice that in cygwin there's no FS type for the mount call. This is a
problem :[.

As I don't know how the mount fs type is set in linux, I'm not going to
suggest how we should do it, but what I need for UMSDOS (unless you want it
either globally on or off) is to be able to get the correct fhandler_* from
a given file path. There's no generic mount based capability in cygwin today
(and that will be needed if we ever want a mountable proc file system :]).
(the logic is straight forward: find the mount point a file belongs to and
lookup the device number from the mount point).

Any objections to mount(win32, posix, flags) becoming mount(win32, posix,
type, flags) ?

if type is NULL, the device number will be the current default of
FH_DISK_FILE.

Rob