[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/include/app.h

@@ -59,8 +59,8 @@ void app_handleButtonPress(int button);
 void app_handleButtonRelease(int button);
 void app_handleWheelMotion(double motion);
 void app_handleKeyboardTyped(const char * typed);
-void app_handleKeyPress(int scancode, int charcode);
-void app_handleKeyRelease(int scancode, int charcode);
+void app_handleKeyPress(int scancode);
+void app_handleKeyRelease(int scancode);
 void app_handleKeyboardModifiers(bool ctrl, bool shift, bool alt, bool super);
 void app_handleKeyboardLEDs(bool numLock, bool capsLock, bool scrollLock);
 void app_handleEnterEvent(bool entered);