[Bugfix] Fix SIGABRT in KqueueSelector

[danielaRiesgo]

Fixes issue #78 , which persisted even with #83 fix.
Our team tried this fix over the #83 , so you may want to merge both of them.
We had a SIGABRT and an EXC_BAD_ACCESS before we made this fix. And after restarting simulater and this fix, the tests run smoothly (we use Embassy for UI tests).

Explanation

The array count was incorrectly used.
The documentation says:

• Warning: Do not rely on anything about the array that is the target of this method during execution of the body closure; it might not appear to have its correct value.

Meaning we should not used kevents array in the closure. But then it continues:

Instead, use only the UnsafeMutableBufferPointer argument to body.

So we should use the pointer provided to body, not the count calculated before the function is called.

[MurrSch]

Hi, is there any chance this will be merged?
This issue blocks me from using Ambassador.
Thanks!

[YanushKhotyan]

Hi!
Is there any chance this will be merged?
Thanks!

[Goos]

Hi @danielaRiesgo, thanks for submitting the PR. Sorry for the late response, this project hasn't been actively maintained. This change looks good though and seems in line with the swift pointer API, so I'll go ahead and merge this.