Combined XInput/DirectInput joystick driver disabled in default allegro5.cfg

[arganoid]

The default allegro5.cfg says "You can choose between the XINPUT or DIRECTINPUT driver for joysticks and force feedback joysticks", and the setting is set to XINPUT by default. But if you comment out this line, you get combined XInput and DirectInput support, which is not mentioned either in the config file or at https://liballeg.org/a5docs/5.2.7/joystick.html - in fact the latter goes so far as to say that the two drivers are mutually exclusive! Should we change this line to be commented out by default, and also update the comments and docs?

I'll do it if no-one is aware of any downsides of doing this.

In wsystem.c, win_get_joystick_driver() has the comment "By default the combined xinput/directinput driver is used unless directinput or xinput exclusive is set", and defaults to _al_joydrv_windows_all if neither of the other options is set.