FAUSTPy: migrate to new FAUST llvm-c-dsp C API.

Migrate to the new FAUST llvm-c-dsp C API.  "llvm-dsp" is part of libfaust and
is basically an LLVM-based embeddable FAUST compiler that returns C++ objects
representing the compiled DSPs.  "llvm-c-dsp" is a C API built on top of that.
Apart from being a nicer approach than compile_faust(), this also makes it
potentially possible to create binary distributions of FAUSTPy.

Also update the test suite to the new FAUSTPy classes.
Tests: simplify test.helpers a bit.
libfaust: slight simplification.
libfaust: define llvm_* types opaquely.
libfaust: remove obsolete typedefs.

Remove typedefs that were necessary because of the way they were defined in the
FAUST headers.  This has now been remedied, so they can be removed.
libfaust: adopt the *Glue definitions from CUI.h.
Remove deprecated UIGlue fields.
Tests: skip a test that crashes python.