Use HTTP URLs instead of FTP URLs in pkg-descr files

The use of FTP URLs in pkg-descr files has been deprecated and some of
the FTP URLs in those files have already become stale.

Replace FTP URLs with HTTP URLs where possible.

There does not appear to be any mirror that preserves the contents of
the defunct ftp.cac.washington.edu host.

Approved by: portmgr (implicit)