Optmization to ccArrayGetIndexOfObject

Optimized loop of ccArrayGetIndexOfObject to remove the overhead of 3
pointer dereferences per iteration, and pre-increment the int for
speed. If this function is called a lot, and with a large list, this
will result in a good performance win.

This can probably be done with just pointers, but I haven't taken the
time to validate all function calls to make sure it would be
appropriate. Though I can guarantee that if this worked fine before, it
will work fine with this change.