(server-with-environment): Simplify.

(server-with-environment): Simplify.
(server-select-display, server-unselect-display): Re-add functions that
seem to have been lost in the multi-tty merge.
(server-eval-and-print, server-create-tty-frame)
(server-create-window-system-frame, server-goto-toplevel)
(server-execute, server-return-error): New functions extracted from
server-process-filter.
(server-execute-continuation): New functions.
(server-process-filter): Restructure so that all arguments are analysed
first and then acted upon in a subsequent stage  This way
server-goto-toplevel can be executed later, when we know if
it's necessary.
Remove the "-version" and "-version-good" support.