lots of core fixes.
took out ppthtml powerpoint convert, it hangs.
dynamic rdbmap to save memory per coll.
fixed disk page cache logic and brought it
back.
stop re-reading if increasing minrecsizes did nothing.
fix tight merges so they work over all colls.
fix merge counting to be fast and not loop over
all rdbbases which could be thousands.
add num mirrors to rebalance.txt.
fix updateCrawlInfo to wait for all replies. critical error!