Branch b1_6

Description: enable data checksumming by default
Details    : enable checksum by default, allow --disable-checksum
 	     configure option and "-o nochecksum" mount option.  Checksums
	     can also be disabled at runtime via $LPROC/osc/*/checksum_pages.
b=13579
i=nathan
i=johann

Minor fixes to get sanity.sh running.