[AD] Issue with DirectInput-only mode

[Andrew Gillett <arg@xxxxxxxxxxxx>]

I've been having problems with both the default combined 
XInput/DirectInput mode and Steam's own input API, as described at:

https://www.allegro.cc/forums/thread/618290

So I decided to try turning off XInput and just use pure DirectInput.

However, I have a 100% reproducible bug when connecting a particular 
pair of controllers. One is an official Xbox 360 controller, the other 
is a cheap 3rd party Xbox 360 controller.

If I start the game with both already connected, or if I connect them 
simultaneously, there is no problem. But if I connect one, then the 
other (the order doesn't matter), one of them will fail to respond to 
inputs - but if I press inputs on the other, it's as if I pressed the 
input on both that controller AND the newly connected controller.

Here is some debug output after enabling DEBUGMODE. I turned off XInput 
by turning off ALLEGRO_CFG_XINPUT.

dinput   I         wjoydxnu.cpp:1003 joystick_enum_callback           [  
17.73569] Joystick 0 initialized, GUID: f8bd5190-fbd6-11e8-8014445535400
dinput   I         wjoydxnu.cpp:1136 joydx_merge                      [  
17.74460] Merged, num joysticks=1
dinput   D         wjoydxnu.cpp:889 joystick_enum_callback           [  
18.83082] Device f8bd5190-fbd6-11e8-8014445535400 still exists
dinput   D         wjoydxnu.cpp:889 joystick_enum_callback           [  
21.93956] Device f8bd5190-fbd6-11e8-8014445535400 still exists
dinput   I         wjoydxnu.cpp:1003 joystick_enum_callback           [  
21.97031] Joystick 1 initialized, GUID: f8c25aa0-fbd6-11e8-8024445535400
dinput   I         wjoydxnu.cpp:1136 joydx_merge                      [  
21.98685] Merged, num joysticks=2
dinput   D         wjoydxnu.cpp:889 joystick_enum_callback           [  
23.14051] Device f8bd5190-fbd6-11e8-8014445535400 still exists
dinput   D         wjoydxnu.cpp:889 joystick_enum_callback           [  
23.14371] Device f8c25aa0-fbd6-11e8-8024445535400 still exists