the headers already sent error means that there is a blank space between php code blocks.
most likely when you paste that line of code into line 1, you have a blank space at the end:
"<?php set_time_limit(0) ?> "
see the following thread for more details:
deleting the line:
if (function_exists("rel2abs")) $WA_redirectURL = $WA_redirectURL?rel2abs($WA_redirectURL,dirname(__ FILE__)):"";
will not cause other problems if the page is not used as a framework builder plugin.