[client] input: add support for evdev keyboard capture mode

The new configuration option `input:evdev` accepts a comma separated
list of `/dev/input/` keyboard devices to use for input when in capture
mode. This makes it possible to capture only a specific keyboard instead
of all keyboards.

client/displayservers/Wayland/wayland.h

@@ -277,6 +277,7 @@ void waylandUncapturePointer(void);
 void waylandRealignPointer(void);
 void waylandWarpPointer(int x, int y, bool exiting);
 void waylandGuestPointerUpdated(double x, double y, double localX, double localY);
+int waylandGetCharCode(int key);
 
 // output module
 bool waylandOutputInit(void);