github pull request #749 by argrath: add support for MSGHANDLER for
WIN32 using spawn() rather than the fork()+exec() used on UNIX.
Closes #749
Unix: support --nethackrc=filename on the command line; same effect as
NETHACKOPTIONS='@filename' but leaves NETHACKOPTIONS available for
specifying options; --no-nethackrc is same as --nethackrc=/dev/null
+Windows: implement MSGHANDLER (pr #749 by argrath)
X11: implement 'selectsaved', restore via menu of saved games
X11: echo getline prompt and response (wishes, applying names) to message
window and dumplog message history