Initial import of csound4-4.23.12.6

Initial import of csound4-4.23.12.6

Csound is a software synthesis package in the tradition of so-called
music-N languages, among which the best-known is Music V.  It consists
of an orchestra- and score-driven executable, written in C for
portability.  Since Csound is a computational language, it is highly
flexible and efficient; complexity is gained only at the expense of
computation time.  Basically Csound reads some files and creates the
result as a file on disk or, on faster machines, through a DAC in real
time.