www/c-icap: update to 0.6.4

Changelog: https://sourceforge.net/p/c-icap/mailman/c-icap-users/?viewmonth=202507

The c-icap-0.6.4 changes:

• Fix memory leak inside ci_mem_inflate API function
• Fix small memory leak inside ci_client_library_release
• Fix to honor the configured KeepAliveTimeout
• Other minor fixes