fix random setsockopt failure (EINVAL)

[Aggelos Economopoulos]

Sepherosa Ziehau wrote:
> Hi all,
> 
> Following patch should fix random setsockopt failure (EINVAL) in HEAD:
> http://leaf.dragonflybsd.org/~sephe/sockopt.diff
> 
> In addition to that:
> - Don't do copyout in setsockopt; the user arg is const
> - Always setup sopt (i.e. set sopt.sopt_val to NULL early)
> - In sys_getsocktopt(), centralize valsize check
> 
> Please review/test it.

Looks good. Feeling a bit embarrassed btw :)

Aggelos