m + posix mqueue

Signed-off-by: Mattias Andrée <maandree@operamail.com>
common api for posix and sysv ipc

Signed-off-by: Mattias Andrée <maandree@operamail.com>
fix small errors

Signed-off-by: Mattias Andrée <maandree@operamail.com>
finish common api for mqueue

Signed-off-by: Mattias Andrée <maandree@operamail.com>
m + z and barriers under -P

Signed-off-by: Mattias Andrée <maandree@operamail.com>