cleanup: general removal of TODO (and similar) comments

They tend to never get updated anyway so they're frequently inaccurate
and we never go back to revisit them anyway. We document issues to work
on properly in KNOWN_BUGS and TODO instead.

lib/easy.c

@@ -646,7 +646,7 @@ static CURLcode wait_or_timeout(struct Curl_multi *multi, struct events *ev)
       return CURLE_RECV_ERROR;
 
     if(mcode)
-      return CURLE_URL_MALFORMAT; /* TODO: return a proper error! */
+      return CURLE_URL_MALFORMAT;
 
     /* we don't really care about the "msgs_in_queue" value returned in the
        second argument */