For an unknown reason the touch pad of my PowerBook generates button 5
events when you operate it. This causes the adb_mouse code to convert
them to button 2 events, which is not what we want.
Add a new flag, AMS_TOUCHPAD, which is used to distinguish the touch
pad. When set, don't convert button events of unknown buttons to the
last button.
There are still three problems left with respect to user input:
- The mouse button events are not properly processed when the touch pad
isn't touched.
- The arrow keys on the keyboard don't work inside X11.
- The power button isn't handled by the kernel, similar to the ACPI
power button on i386/amd64.
Approved by: nwhitehorn
8df5c9ee67