Display man pages immediately and use process-filter to format them asynchronously.

Display man pages immediately and use process-filter to format them asynchronously.
* lisp/man.el (Man-width): Doc fix.
(man): Doc fix.
(Man-start-calling): Use `with-selected-window' to get
`frame-width' and `window-width'.
(Man-getpage-in-background): Call `Man-notify-when-ready'
immediately after creating a new buffer.  Call `Man-mode' and set
`mode-line-process' in the created buffer.  Set process-filter to
`Man-bgproc-filter' in start-process branch.  In call-process branch
call either `Man-fontify-manpage' or `Man-cleanup-manpage'.
Use `Man-start-calling' inside `with-current-buffer'.
(Man-fontify-manpage): Don't print messages.  Fix boundary condition.
(Man-cleanup-manpage): Don't print messages.
(Man-bgproc-filter): New function.
(Man-bgproc-sentinel): Add `save-excursion' to keep point when
user moved it during asynchronous formatting.  Move calls of
`Man-fontify-manpage' and `Man-cleanup-manpage' to
`Man-bgproc-filter'.  Move the call of `Man-mode' to
`Man-getpage-in-background'.  Use `quit-restore-window'
instead of `kill-buffer'.  Use `message' instead of `error'
because errors are catched by process sentinel.
(Man-mode): Move calls of `Man-build-page-list',
`Man-strip-page-headers', `Man-unindent', `Man-goto-page' to
`Man-bgproc-sentinel'.  Doc fix.  (Bug#2588, bug#5054, bug#9084, bug#17831)