Added configuration for PLAIN security

* ZMQ_PLAIN_SERVER, ZMQ_PLAIN_USERNAME, ZMQ_PLAIN_PASSWORD options
* Man page changes to zmq_setsockopt and zmq_getsockopt
* Man pages for ZMQ_NULL, ZMQ_PLAIN, and ZMQ_CURVE
* Test program test_security

include/zmq.h

@@ -253,6 +253,13 @@ ZMQ_EXPORT int zmq_msg_set (zmq_msg_t *msg, int option, int optval);
 #define ZMQ_XPUB_VERBOSE 40
 #define ZMQ_ROUTER_RAW 41
 #define ZMQ_IPV6 42
+#define ZMQ_MECHANISM 43
+#define ZMQ_PLAIN_SERVER 44
+#define ZMQ_PLAIN_USERNAME 45
+#define ZMQ_PLAIN_PASSWORD 46
+#define ZMQ_CURVE_SERVER 47
+#define ZMQ_CURVE_PUBLICKEY 48
+#define ZMQ_CURVE_SERVERKEY 49
 
 /*  Message options                                                           */
 #define ZMQ_MORE 1
@@ -261,6 +268,11 @@ ZMQ_EXPORT int zmq_msg_set (zmq_msg_t *msg, int option, int optval);
 #define ZMQ_DONTWAIT 1
 #define ZMQ_SNDMORE 2
 
+/*  Security mechanisms                                                       */
+#define ZMQ_NULL 0
+#define ZMQ_PLAIN 1
+#define ZMQ_CURVE 2
+
 /*  Deprecated aliases                                                        */
 #define ZMQ_DELAY_ATTACH_ON_CONNECT ZMQ_IMMEDIATE
 #define ZMQ_NOBLOCK                 ZMQ_DONTWAIT