Fixes missing keycodes, cleans up & sorts existing ones.

 An essential/prerequisite commit for further Input improvements, e.g. #2524
Merge branch 'master' of https://github.com/libgdx/libgdx

Conflicts:
	gdx/src/com/badlogic/gdx/Input.java
Merge pull request #2575 from vaxquis/master

fixes missing keycodes, cleans up & sorts existing ones - an essential/p...