ex_joystick_events: Fix layout for long stick/axis/button names.
Initial haptics API. Only implemented on Linux to begin with.

With modifications from me (Peter).
Allow X11 port to build without Linux haptics driver.
Add assertions at top-level of haptics API.
Actually reserve a effects slot in the Linux haptics driver.
Fix bug where a stale haptic effect structure could be dereferenced.
Zero out ff_effect (reported by valgrind).
docs: Link to haptics documentation.
docs: Add Since: markers for haptics documentation.