Compile errors in libgcj while building cross-compiler for MinGW

[Tom Tromey]

>>>>> "Adam" == Adam Megacz <gcj@lists.megacz.com> writes:

Adam> I would greatly prefer to simply break off the Win32 socket
Adam> stuff into Win32SocketImpl.java, just like we do with filesystem
Adam> stuff.  The Win32 sockets stuff superficially appears to be
Adam> BSD-compatible, but it's not.

This sounds like a good plan to me.
We can also put the disable-java.net code into its own files as well.

Incidentally I've noticed there is still some unix-centric code in
File.java.  Do you Win32 guys want PRs for this?  I think
getAbsolutePath() is probably buggy, getParent() definitely is, and
toURL() definitely is (it needs to change the separator).

Tom