In snapshot 2000-10-22-0645, configuring with
curl (7.4.1 from source) support:

url.c: In function `php_minit_curl':
curl.c:137: warning: passing arg 1 of
 `zend_register_list_destructors_ex' from incompatible pointer type
curl.c: At top level:
curl.c:789: conflicting types for `_php_curl_close'
curl.c:58: previous declaration of `_php_curl_close'
make[3]: *** [curl.lo] Error 1
make[3]: Leaving directory `/usr/src/php4 200010220645/ext/curl'
make[2]: *** [all-recursive] Error 1
...

There was a mega patch to curl.c a couple of days ago
that perhaps has something to do with this.

4.0.3pl1 was fine with curl.