[PATCH] strstrip remove last blank fix

strstrip() does not remove the last blank from strings which only consist
of blanks.

Example:
char string[] = "  ";
strstrip(string);

results in " ", but should produce an empty string!

The following patch solves this problem:

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@de.ibm.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by Joern Engel <joern@wh.fh-wedel.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>