fix incorrect (and conflicting on LP64 archs) types for sysv ipc msgq functions

include/sys/msg.h

@@ -30,7 +30,7 @@ struct msqid_ds
 
 int msgctl (int, int, struct msqid_ds *);
 int msgget (key_t, int);
-int msgrcv (int, void *, size_t, long, int);
+ssize_t msgrcv (int, void *, size_t, long, int);
 int msgsnd (int, const void *, size_t, int);
 
 #endif

src/ipc/msgsnd.c

@@ -3,7 +3,7 @@
 #include "ipc.h"
 #include "libc.h"
 
-ssize_t msgsnd(int q, const void *m, size_t len, int flag)
+int msgsnd(int q, const void *m, size_t len, int flag)
 {
 	ssize_t r;
 	CANCELPT_BEGIN;