Merge pull request #3789 from std-any-emplace/master

Some minor documentation fixes

doc/zmq_getsockopt.txt

@@ -786,8 +786,8 @@ Applicable socket types:: all, when using TCP transports.
 ZMQ_THREAD_SAFE: Retrieve socket thread safety
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The 'ZMQ_THREAD_SAFE' option shall retrieve a boolean value indicating whether
-or not the socket is threadsafe. Currently 'ZMQ_CLIENT' and 'ZMQ_SERVER' sockets
-are threadsafe.
+or not the socket is threadsafe. See linkzmq:zmq_socket[3] for which sockets are
+thread-safe.
 
 [horizontal]
 Option value type:: boolean

doc/zmq_setsockopt.txt

@@ -1154,8 +1154,8 @@ Default value:: NULL
 Applicable socket types:: ZMQ_XPUB
 
 
-ZMQ_ONLY_FIRST_SUBSCRIBE: Process only fist subscribe/unsubscribe in a multipart message
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ZMQ_ONLY_FIRST_SUBSCRIBE: Process only first subscribe/unsubscribe in a multipart message
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 If set, only the first part of the multipart message is processed as
 a subscribe/unsubscribe message. The rest are forwarded as user data
 regardless of message contents.