roomname: use UID in default roomname

Use the UID of the xmppipe process instead of the PID in the default
name. This allows many processes running under the same user on a host
to share the same output channel and makes it easier to pre-create the
MUC if the xmppipe XMPP user does not have MUC creation privs.

README.md

@@ -90,7 +90,7 @@ Options
 -o *output*
 :   XMPP MUC name
 
-    Default: stdout-*hostname*-*pid*
+    Default: stdout-*hostname*-*uid*
 
 -S *subject*
 :   XMPP MUC subject

src/xmppipe_util.c

@@ -208,7 +208,7 @@ xmppipe_roomname(char *label)
     }
     name[sizeof(name)-1] = '\0';
 
-    (void)snprintf(buf, len, "%s-%s-%d", label, name, getpid());
+    (void)snprintf(buf, len, "%s-%s-%d", label, name, getuid());
 
     return buf;
 }