[Pipet Users] Overflow (PL) updates

[Jean-Marc Valin]

Hi everyone,

A lot has been going on in the Overflow CVS and I'm soon planning to
make a new release. Lots of the changes concern ease of use. Here's a
qui list of changes:

- The VFLOW_PATH environment variable is no longer required (it's
determined from the --prefix configure option)

- What was in libflowui is now in the same library than the one called
libnetwork. The new library is now called libflow and is all that needs
to be linked with Piper.

- The FFTW library is no longer required to build Overflow. If you don't
have it, the build will continue without FFT support.

- It's now possible to have Feedback loops in a flow. This is done by
using the "Feedback" node and a demo is available in the examples
directory.

- Overflow also supports throwing and catching exceptions within the
flow using the "Throw" and "Catch" node. This is still undocumented.


Some of these changes will require modifications to Piper, mostly in the
makefiles/configure.in, though. I suggest someone gets the current
Overflow version in CVS and tries to build Piper with it, so that the
next version I release works well with Piper.

	Jean-Marc