- Document the -p and -l options in split-window.

- Update {copy,scroll}-mode with the -u option.
- While there sort options alphabetically.

TODO

@@ -87,9 +87,7 @@
 (hopefully) for 0.7, in no particular order:
 - key to switch to copy mode from scroll mode
 - attach should have a flag to create session if it doesn't exist
-- document -u flag to scroll-mode/copy-mode
 - document suspend-client
 - document command sequences
 - document find-window
-- document split-window -p and -l
 - document window-status-{fg, bg, attr}