winewayland.drv: Support mouse buttons 4 and 5.
Map linux mouse buttons to win32 XBUTTON1 and XBUTTON2. Although BTN_SIDE and BTN_EXTRA are the typical event codes for these buttons, some drivers use BTN_BACK and BTN_FORWARD, so map both pairs.
Map linux mouse buttons to win32 XBUTTON1 and XBUTTON2. Although BTN_SIDE and BTN_EXTRA are the typical event codes for these buttons, some drivers use BTN_BACK and BTN_FORWARD, so map both pairs.