[RFC] libosmocore: New libosmosdr sub library

Hi, I've just pushed a libosmosdr sublibrary in a sylvain/sdr branch in the libosmocore git. Currently it contains mostly a complex vector 'class' along with various math functions used on them (convolution / correlation / ...). Some aspects the the API along with some of the underlying math are inspired by the code from openbts, but it is a complete rewrite in pure C with some aspects simplified, and some others extended. If anybody has comments before I merge it in master, they're welcome. The doxygen doc should be clear enough (and even includes fancy latex equation :P) Cheers, Sylvain