bsd-user: Add target_to_host_msqid_ds for msgctl(2)

Add target_to_host_msqid_ds() to convert target struct msqid_ds to host
format for msgctl(2) IPC_SET operations. Uses memset to zero the struct
rather than directly accessing kernel-only members. Handles FreeBSD
64-bit time_t except on i386.

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Brooks Davis <brooks@one-eyed-alien.net>
Signed-off-by: Sean Bruno <sbruno@FreeBSD.org>
Signed-off-by: Mikael Urankar <mikael.urankar@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>