Fixed a few new build warnings against the OS X 10.9 API.
Updated keyboard preferences helptext and hotkey warning to account for 10.9's new per-app accessibility controls. Added first-run check for hotkey capture support advising users to enable the relevant accessibility control for best results.
Updated standard Boxer helpbook with appropriate instructions for overriding hotkeys on 10.9. Migrated helpbook to use proper x-help-script:// links.
Updated standalone help file with equivalent instructions for overriding hotkeys on 10.9. Backported some rewritten keyboard and mouse helptext from there to the standard help file. Removed unused scripts from standalone help file.