This patch is to offer common accounting data collection method at memory
usage for various accounting packages including BSD accounting, ELSA, CSA
and any other acct packages that use a common layer of data collection.

New struct fields are added to mm_struct to save high watermarks of rss
usage as well as virtual memory usage.

New struct fields are added to task_struct to collect accumulated rss usage
and vm usages.

These data are collected on per process basis.
Signed-off-by: Jay Lan <jlan@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>