1. Resolve the "hidden symbol 'atexit' ... being referenced by DSO" error
   by using the -shared option (link against shared objects, not static libs)
2. The path to the xpdev output directory (where to find libxpdev.a) is just
   wrong. Hard-coded the machine architecuture portion (.x64) as a hack for
   now. Also, since this is use the LD macro, you need to pass "LD=gcc" on the
   make command-line. Not sure how this worked before.

Fixes (or at least works-around) issues reported by Ryan Fantus (1:218/820)

It's not unlikely that any utilities using SDL will have new issues... you
may want to hold off on updates for a bit until this settles unless you
don't use SDL mode.

keys.

COM0:STDIO <- Indicates that stdio should be used.
COM0:SOCKET### <- Indicates socket I/O should be used with socket handle ###
COM0:HANDLE### <- Indicates Win32 COM should be used with COM handle ###

SSH.  Passing a socket isn't very likely to be helpfull, and a local socket
pair seems like a kludge (That will, of course, be supported for "old-style"
32-bit doors)

instead of *((WORD *)var).

which will break the ability to drop in an updated library and have the door
Just Work.