Comments and style(9) only, no functional changes.
kqueue: Change error for kqueues rlimit from EMFILE to ENOMEM and document
this error condition in the kqueue(2) manual page.

Discussed with:	kib
During code inspection, I spotted that there was a code path where
CLNT_CONTROL() would be called on "client" after it was
released via CLNT_RELEASE(). It was unlikely that this
code path gets executed and I have not heard of any problem
report caused by this bug. This patch fixes the code so that
this cannot happen.

MFC after:	2 months