Convert macros to functions to let type safety do its thing. Switch
some functions from ints to more appropriate bool. Move all forward
declarations together to top of the #ifdef __KERNEL__ section. Use
kernel-doc format for comments.
Some macros couldn't be converted because they use functions from
security.h which sometimes are extern and sometimes static inline,
and we don't want to #include security.h in capability.h.
Also add a real current_user_ns function (and convert the existing
macro to _current_user_ns() so we can use it in capability.h
without #including cred.h.
Signed-off-by: Serge E. Hallyn<serge.hallyn@xxxxxxxxxxxxx>