a potential bug in Layer.

https://github.com/cocos2d/cocos2d-x/issues/2948
Update CCLayer.cpp

change "_accelerometerEnabled = false"
to "setAccelerometerEnabled(false)"
in method init().
a potential bug in ScrollView

check _touches in setTouchEnabled
Fix for #2892.
1. Updatet the API documentation and parameter name from "object" to "sender" to reflect it's true purpose.
2. Fixed addObserver and observerExisted because it didn't allowed to add observers to notifications that only differs by sender
Fix for #2892.
3. Fixed registerScriptObserver method.
Fixed broken links and wrong encoding in the doc.

Fixed Obj-C names when referening functions.
Changed some GB2312 encoded characters to UTF-8.
Changed two 'XXX class for cocos2d for iphone'.
Documentation & Cocos2d-x C++ Style
Merge pull request #3404 from timothyqiu/docfix

Documentation fix: broken links and wrong encoding in the doc...
Let CCDirector set all GL state
Merge pull request #2950 from zcgit/develop

a potential bug in Layer.
Update AUTHORS
Merge pull request #3439 from folecr/android_rendering_bugfix

Let CCDirector set all GL state in the Android port
Merge pull request #3285 from gkosciolek/fix_for_CCNotificationCenter

closed 2611: Fixing the bug that observers with the same target and selector but different sender are the same observer in NotificationCenter.
Update AUTHORS [ci skip]