This releases changes the IO:* modules (formerly part of libxml) to
use exceptions for error reporting. At the same time, channel methods
are modified to be much closer to their C counterparts. They
implement buffered file access, blocking and non-blocking IO on TCP
sockets, and select()-ing on a set of channels. The new classes are
incompatible to the old Channel module.
Tiny update, removing the gcc-ism of zero length arrays from module descriptors.