Stats

Stats logged for fetches, reads, writes, etc in scstats btree files - one global per process and one for each mmap'd file along with tests for information

Three new methods - clearglobalstats resets the global stat file (can't just delete a file in process), getglobalstats gets stat info from global file as an array and getstats gets local stat info as an array

globals in PHP are now handled through ginit/gshutdown instead of the older style of setup, and tests clean up after themselves properly - so scstats files are removed as well as cache files