Move input-related files into core/input

This commit moves all the input-related files from `core/`
to `core/input/`, and renames a couple as relevant
(input.js --> input/devices.js, keyboard.js --> input/util.js).

LICENSE.txt

@@ -8,8 +8,8 @@ is not limited to):
     core/base64.js
     core/des.js
     core/display.js
-    core/input.js
-    core/keysym.js
+    core/input/devices.js
+    core/input/keysym.js
     core/logo.js
     core/playback.js
     core/rfb.js
@@ -17,7 +17,7 @@ is not limited to):
     core/util.js
     core/websock.js
     app/webutil.js
-    core/xtscancodes.js
+    core/input/xtscancodes.js
 
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