ovs-appctl: Add "version" command to print version of running daemons.

When debugging a running system, we occasionally see a mismatch of
different versions because someone forgets to restart one or more
daemons.  Often times, it would be useful to know what's running as
opposed to what's on the current runpath.

ChangeLog

@@ -1,6 +1,7 @@
 Post-v1.2.0
 ------------------------
-
+    - ovs-appctl:
+      - New "version" command to determine version of running daemon
 
 v1.2.0 - 03 Aug 2011
 ------------------------

lib/unixctl.c

@@ -107,6 +107,13 @@ unixctl_help(struct unixctl_conn *conn, const char *args OVS_UNUSED,
     ds_destroy(&ds);
 }
 
+static void
+unixctl_version(struct unixctl_conn *conn, const char *args OVS_UNUSED,
+                void *aux OVS_UNUSED)
+{
+    unixctl_command_reply(conn, 200, get_program_version());
+}
+
 void
 unixctl_command_register(const char *name, unixctl_cb_func *cb, void *aux)
 {
@@ -206,6 +213,7 @@ unixctl_server_create(const char *path, struct unixctl_server **serverp)
     }
 
     unixctl_command_register("help", unixctl_help, NULL);
+    unixctl_command_register("version", unixctl_version, NULL);
 
     server = xmalloc(sizeof *server);
     list_init(&server->conns);

utilities/ovs-appctl.c

@@ -88,6 +88,7 @@ Targets:\n\
   -t, --target=TARGET  pidfile or socket to contact\n\
 Common commands:\n\
   help               List commands supported by the target\n\
+  version            Print version of the target\n\
   vlog/list          List current logging levels\n\
   vlog/set MODULE[:FACILITY[:LEVEL]]\n\
       Set MODULE and FACILITY log level to LEVEL\n\
@@ -97,7 +98,7 @@ Common commands:\n\
   vlog/reopen        Make the program reopen its log file\n\
 Other options:\n\
   -h, --help         Print this helpful information\n\
-  -V, --version      Display version information\n",
+  -V, --version      Display ovs-appctl version information\n",
            program_name, program_name);
     exit(EXIT_SUCCESS);
 }