Add new line of /proc/meminfo output.

Explain the HugePage_ lines in /proc/meminfo (from Bill Irwin).

Change KB to kB since the latter is what is used in the kernel.
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>