Fix warning for comparing enum

CC user.c
user.c:202:15: warning: comparison of unsigned
      enum expression < 0 is always false
      [-Wtautological-compare]
        if (c < 0 || c >= CONN_MAX)
            ~ ^ ~

src/common.h

@@ -104,7 +104,7 @@ struct query {
 };
 
 enum connection {
-        CONN_RAW_UDP,
+        CONN_RAW_UDP = 0,
         CONN_DNS_NULL,
         CONN_MAX
 };

src/user.c

@@ -199,7 +199,7 @@ user_set_conn_type(int userid, enum connection c)
         if (userid < 0 || userid >= usercount)
                 return;
 
-        if (c < 0 || c >= CONN_MAX)
+        if (c < CONN_RAW_UDP || c >= CONN_MAX)
                 return;
 
         users[userid].conn = c;