Improve hack to "determine" if APR supports thread-safe pollsets by hiding the

Improve hack to "determine" if APR supports thread-safe pollsets by hiding the
presence of kqueue() on Leopard, matching APR's configuration.

Event and Simple no longer report that they are supported on Leopard, resolving
a broken default config file with --enable-mpms-shared=all on that platform.
(Event was loaded by default in httpd.conf, and it failed at startup when it
failed to obtain a thread-safe pollset.)

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@836165 13f79535-47bb-0310-9956-ffa450edef68