[PSX] Pokopom Xinput Pad Plugin v2.0 r51

Pokopom is a pad plugin that emulates a DualShock1 and DualShock2 controller for PS1 and PS2 emulators. It only uses XInput, so as  to avoid the DirectInput troubles with X360 controllers. It currently has only some basic configuration dialog, and defaults to use the first and second XInput controllers as pad1 and pad2 respectively.  The plugin supports rumble with a nice custom curve, and has extended analog stick range to cover the 'square' on PSX's controllers.