Avoid Groff hanging on MS-Windows when invoked by "M-x man"
* lisp/man.el (Man-build-man-command): On MS-Windows, redirect stdin of 'man' to the null device, to make sure Groff exits immediately after formatting the man page.
* lisp/man.el (Man-build-man-command): On MS-Windows, redirect stdin of 'man' to the null device, to make sure Groff exits immediately after formatting the man page.