Revised KeyList for clarity
Merge branch 'master' of git://github.com/Ragnar-F/AutoHotkey_L-Docs
KeyList - Remove obsolete OS notes and correct tense

AutoHotkey itself requires Windows 2000/XP or later.
Required (past) -> Requires (present).
KeyList - code tags
KeyList - Add detail for Launch_App1/2
KeyList - Add hotkey prefix corresponding to each modifier key
KeyList - Add detail for XButtons and WheelLeft/Right