Runmode fixes and cleanups

Bug #939: thread name buffers are sized inconsistently
These buffers are now all fixed at 16 bytes.

Bug #914: Having a high number of pickup queues (216+) makes suricata crash
Fixed so that we can now have 256 pickup queues, which is the current built-in
maximum. Improved the error reporting.

Bug #928: Max number of threads
Error reporting improved. Issue was the same as #914.