docs: bring four more man pages closer to standard formatting

docs: bring four more man pages closer to standard formatting

In the IPC man pages strictly adhere to the memory, queue, semaphore
order, to reduce disorientation.  And for 'ipcmk', the arguments for
-M and -S and -p are not optional.  Add --version for 'mountpoint'.

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>