The DUP System

In addition to fixing various bugs (see ChangeLog), this release improves the performance of most filters, especially for long lines of input, adds support for writing a PID file to dupd, increases the number of file descriptors to 65536 (overriding FD_SETSIZE), fixed various performance issues in dup to dupd communication and also adds caching of DNS lookups to dupd. The language and network protocol are entirely backwards-compatible, the main changes for this release either improve performance or fix (largely minor) bugs.