Patrick Monnerat and I modified libcurl so that now it *copies* all strings

Patrick Monnerat and I modified libcurl so that now it *copies* all strings
passed to it with curl_easy_setopt()! Previously it has always just refered
to the data, forcing the user to keep the data around until libcurl is done
with it. That is now history and libcurl will instead clone the given
strings and keep private copies.