msgctl{08, 09, 10, 11}: cleanup

 * Moved common functions, definitions to libmsgctl.h, libmsgctl.c.
 * Changed tst_* in the children with printf + exit (or return).
 * Some cleanup.

Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>
7 files changed