include/linux/utsrelease.h and include/linux/version.h aren't removed any
more by mrproper in kernel 2.6.20-rc2.  The patch below fixes this.

The definition of MRPROPER_FILES looks weird: generated-headers looks like
a misspelling of generated_headers, but that one is a Makefile target, not
a variable or a file, so I don't see how including it in MRPROPER_FILES
could have any effect.
Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>