Remove implementation-defined sentences.

lib/libc/sys/mq_open.2

@@ -52,27 +52,17 @@ descriptor is used by other functions to refer to that message queue.
 The
 .Fa name
 argument points to a string naming a message queue.
-It is unspecified
-whether the name appears in the file system and is visible to other functions
-that take pathnames as arguments.
 The
 .Fa name
-argument conforms to the construction rules for a pathname.
-If
+argument should conform to the construction rules for a pathname.
+The
 .Fa name
-begins with the slash character, then processes calling
+should begin with a slash character. Processes calling
 .Fn mq_open
 with the same value of
 .Fa name
 refers to the same message queue object, as long as that name has not been
 removed.
-If
-.Fa name
-does not begin with the slash character, the effect is implementation-defined.
-The interpretation of slash characters other than the leading slash character
-in
-.Fa name
-is implementation-defined.
 If the
 .Fa name
 argument is not the name of an existing message queue and creation is not

lib/libc/sys/mq_receive.2

@@ -69,12 +69,6 @@ and copied to the buffer pointed to by the
 .Fa msg_ptr
 argument.
 .Pp
-If the value of
-.Fa msg_len
-is greater than
-.Brq Dv SSIZE_MAX ,
-the result is implementation-defined.
-.Pp
 If the argument
 .Fa msg_prio
 is not

lib/libc/sys/mq_setattr.2

@@ -56,9 +56,8 @@ structure will be set to the specified values upon successful completion of
 .Fn mq_setattr :
 .Bl -tag -width ".Va mq_flags"
 .It Va mq_flags
-The value of this member is the bitwise-logical OR of zero or more of
-.Dv O_NONBLOCK
-and any implementation-defined flags.
+The value of this member is zero or
+.Dv O_NONBLOCK .
 .El
 .Pp
 The values of the