Handle up to 63 partitions per drive

Revamp device parsing code.  Introducing support for more partitions
into the shilka-generated parser has the unfortunate side-effect of
raising the size of the DLL by almost 2 Megs.  Therefore we split out
the handling for /dev/sdXY devices into a tiny bit of hand-written
code.

While at it, remove some unused cruft from devices.* and generally
clean up the device class to provide access methods instead of direct
access to members.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/mmap.cc

@@ -528,7 +528,8 @@ mmap_record::alloc_fh ()
      of the correct type to be sure to call the method of the
      correct class. */
   device fdev;
-  fdev.name = fdev.native = "";
+  fdev.name ("");
+  fdev.native ("");
   fdev.parse (get_device ());
   fhandler_base *fh = build_fh_dev (fdev);
   if (fh)