Commit Waffle libraries for first rough-cut SSPI support

By committing the libraries to the tree it's easier to manage development. This
probably won't fly for a release in PgJDBC upstream, we'll need to use maven-ant-tasks
to fetch them when Waffle is conditionally enabled.
Add SSPI support to PgJDBC

The actual implementation is fairly clean, but the integration into PgJDBC's
build leaves a bit to be desired.

The Waffle libraries aren't bundled within the PgJDBC jar, so you must add them
to your classpath separately. We'll probably want an ant task to produce a
'fat' jar driver.

The build support isn't conditional, so it adds a hard dependency on waffle-jni
to PgJDBC. I'll need to instead make it conditional and probably fetch Waffle
from Maven via maven-ant-tasks if enabled.

I'll also need to ensure that the JDBC driver, when compiled with Waffle
support for SSPI, still loads and runs without error if Waffle isn't present or
the platform isn't compatible, and fails in a graceful and informative manner.
At present this is untested.

Finally, the driver currently treats SSPI as equivalent to GSSAPI and tries to
do Kerberos authentication directly against the remote server. (This can work
if spnego is requested and the correct kerberos principal etc are supplied as
JDBC params but it requires re-authentication, it doesn't use the existing
Windows credentials).

In case anyone is relying on doing Kerberos negotiation with a PostgreSQL
server in sspi authentication mode I'll need to add a URL parameter to force
the old mode to be used, and to default to that if Waffle isn't available or we
aren't on Windows. Or only use the new mode when explicitly requested by a URL
parameter.
Add debug message tracing SSPI target name