This provides the program to compute power spectral density and evaluate
coherency properties of pairs and triples of input channels

The GSL random number generators were seeded with the value of the wall clock
second. When requeting several sequences of random numbers, they turned out to
be identical, because each time the random number generator got seeded with
the same value.

The new version accepts seed values set through the environment variable
GSL_RNG_SEED and, if not set, uses the nanosecond value of the wall clock
together with the seconds to ensure different seed for different calls to the
functions.

random number generator returns identical sequences, because it is repeatedly
seeded with them seconds value (execution is too fast to take place at
different wall clock seconds)