Fix bug: CCControl's touch priority is not set correctly; m_nDefaultTouchPriority is never used;
m_nDefaultTouchPriority is never used anymore; Instead, we setTouchPriority(1) directly for all CCControl by default.
Merge pull request #2251 from tiantian20007/master

fixed #1937: CCControl's touch priority is not set correctly; m_nDefaultTouchPriority is never used;