Add quick-cocos2d-x  support, and fix minor bug.

Add quick-cocos2d-x support.
To enable quick-cocos2d-x support, simply uncomment the line commented
in preDB.h.
abs(),FLT_MAX can't be found without add <float.h> and <stdlib.h> in
some platforms.
Added a header that included all of DragonBones relevant files.