Improve ioqueue performance on multithreadeded environment

[nanang]

This ticket will apply the following updates on the ioqueue (most affected implementations are select & epoll):

• Protection against high fds (i.e: fd > FD_SETSIZE) in ioqueue socket registration to avoid potential memory corruption caused by select().
• Added new ioqueue API pj_ioqueue_trylock_key().
• Event dispatcher functions should not wait if an ioqueue key mutex is locked by another thread (perhaps the event for the key is being processed by that thread), skip this key and process next ioqueue key.

Thank you Christian Ambach for the patches.

[nanang]

In 5194:

Close #1894: Improve ioqueue performance on multithreadeded environment.

[nanang]

In 5196:

Re #1894: Fixed high socket descriptor check in ioqueue select, it should be against FD_SETSIZE instead of PJ_IOQUEUE_MAX_HANDLES, as PJ_IOQUEUE_MAX_HANDLES can be lower than FD_SETSIZE.