GunCon overhaul

GunCon overhaul

-Add Trigger, Reload, Aux A, and Aux B as mappable buttons in RetroArch menu for players 1 and 2.

-GunCon trigger, A, and B buttons are mapped to Gun Trigger, Gun Aux A, and Gun Aux B instead of hard coded to left click, right click, and middle click.

-Force cursor to corner of screen for offscreen reload so that reloading works on all four edges of the screen.

-Allow Gun Reload RetroArch input to emulate an offscreen shot.

-Switch gun coordinates from "Pointer" type to "Lightgun" type.