refs #5710 add counters for the number of bytes read and time spent doing IO, for the various ways you can do a fetch. improve the name of get_tokutime() and get rid of the now defunct toku_current_time_nanoseconds()


git-svn-id: file:///svn/toku/tokudb@50481 c7de825b-a66e-492c-adef-691d508d4ae1