Add a new strstrip() function to lib/string.c for removing leading and
trailing whitespace from a string.

Cc: Michael Holzheu <holzheu@de.ibm.com>
Acked-by: NIngo Oeser <ioe-lkml@rameria.de>
Acked-by: NJoern Engel <joern@wohnheim.fh-wedel.de>
Cc: Corey Minyard <minyard@acm.org>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Acked-by: NMichael Holzheu <HOLZHEU@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>