msgctl.2, semctl.2, shmctl.2, svipc.7: Don't mention that ipc_perm is defined in <sys/ipc.h>

There's no need to mention that the 'ipc_perm' structure
is defined in <sys/ipc.h>. That's an implementation detail,
and furthermore <sys/ipc.h> is itself included by the other
System V IPC header files. The current text might lead the
reader to conclude that they must include <sys/ipc.h>, which
is not the case (it is required neither on Linux, nor by the
standards).

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/msgctl.2

@@ -75,7 +75,7 @@ struct msqid_ds {
 .PP
 The
 .I ipc_perm
-structure is defined in \fI<sys/ipc.h>\fP as follows
+structure is defined as follows
 (the highlighted fields are settable using
 .BR IPC_SET ):
 .PP

man2/semctl.2

@@ -93,7 +93,7 @@ struct semid_ds {
 .PP
 The
 .I ipc_perm
-structure is defined in \fI<sys/ipc.h>\fP as follows
+structure is defined as follows
 (the highlighted fields are settable using
 .BR IPC_SET ):
 .PP

man2/shmctl.2

@@ -81,7 +81,7 @@ struct shmid_ds {
 .PP
 The
 .I ipc_perm
-structure is defined in \fI<sys/ipc.h>\fP as follows
+structure is defined as follows
 (the highlighted fields are settable using
 .BR IPC_SET ):
 .PP

man7/svipc.7

@@ -47,9 +47,7 @@ to store information needed in determining permissions to perform an
 IPC operation.
 The
 .I ipc_perm
-structure, defined by the
-.I <sys/ipc.h>
-system header file, includes the following members:
+structure includes the following members:
 .in +4n
 .nf