[PATCH] unexport get_wchan

The only user of get_wchan is the proc fs - and proc can't be built modular.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>