WIP: add basic slab allocation for queue links

allocating 31 links at a time and just shuffling them between several linked lists
two list pointers allow read threads to remove from list head without disturbing
ability of parse thread to traverse the list.  Since only the parse thread sets the ->next
pointer and only the read threads set the ->free pointer.  caveat: parse thread doesn't reap
the first link in the instances' free list, and instances don't free the first link in their
queue without first getting the read mutex.
retrieve system pagesize on startup for later use
WIP: better handling of special files

all specials begin with ..
added ..status with sample output
all config options appear as .. symbolic links pointing back to mount dir
eg. ..clustersize=1 -> .
this should help fix issue with tab completion, but more work needed (TODO)