list: add list_next and list_prev helpers.

Some way towards iterating in the middle of the list.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
endian/short_types: sparse support.

If you're doing endian work, sparse's bitwise annotation is extremely useful.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
short_types: update documentation on be32/le32 etc.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
endian: add documentation on endian typedefs.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>