[Traverso-devel] cmake updates

[Remon]

Hi,

I've added checks for all the libraries/headers that are required or requested 
to the cmake build scripts.

Also updated the internal slv2 code to version 0.2.0 (I think that also means 
that the swh plugins no longer work, unless you compile the newest version)

cmake uses a cache, so when you change certain settings, please do a rm 
CMakeCache.txt first (and then change the settings)

Configuration can be done reasonably easy now with

$ ccmake .

It shouldn't list anything, until after you hit the c key.
Now you can change the features that should be compiled (like PortAudio 
support, mp3 encoding, LV2 support (using either the internal library or a 
system installed one) etc)

I tried to make the header/library checking simple with clear messages what is 
wrong, what needs to be done.
If it still needs improvements, let me know please!

Thanks,

Remon