[PATCH] Add warning `init=' to init/main.c

I passed init=/mylinuxrc to the kernel on the command line.  The kernel
silently dropped down to exec /sbin/init.  It turned out that /mylinuxrc
had improper permissions.  Without any warning message from the kernel that
something was wrong it took awhile to find the issue.  The patch below adds
a warning.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>