Prefer autoregen -ivf to manual autogen.sh

Suggested by Ralph Castain
Take generated files out of git; add correct m4 magic for libtool to auto* files
Avoid truncating huge values for content-length
Fix a bug that could allow dns requests with duplicate tx ids

Spotted by Marko Kreen
Check for POLLERR, POLLHUP and POLLNVAL for Solaris event ports
Defensive programming to prevent (hopefully impossible) stack-stomping