Moved request helpers out to core library.

This didn't actually depend on FCGI any more, and is needed for
request processing from the (WIP) test processor, so it needed to
be in the core library instead of just compiled in along with
main.
Updated autoconf-archive Boost scripts, added filesystem.

The Boost filesystem library is needed for the new test harness.
Fixed bugs in staticxml backend.
Added first 'core' test case.

It is empty at the moment, and does nothing other than test that
the test works without crashing.