msgrcv07: Include lapi/msg.h to fix build

Broken on old distros (CentOS 6 and 7) and on musl (Alpine):

msgrcv07.c:121:46: error: 'MSG_COPY' undeclared (first use in this function)

Signed-off-by: Petr Vorel <pvorel@suse.cz>
diff --git a/testcases/kernel/syscalls/ipc/msgrcv/msgrcv07.c b/testcases/kernel/syscalls/ipc/msgrcv/msgrcv07.c
index 00a7716..2c687c5 100644
--- a/testcases/kernel/syscalls/ipc/msgrcv/msgrcv07.c
+++ b/testcases/kernel/syscalls/ipc/msgrcv/msgrcv07.c
@@ -30,6 +30,7 @@
 #include "tst_test.h"
 #include "tst_safe_sysv_ipc.h"
 #include "libnewipc.h"
+#include "lapi/msg.h"
 
 #define MSGTYPE1	1
 #define MSGTYPE2	2