gnuradio fosphor block (GPU spectrum display)

 This implements a GNU Radio sink consisting of a GL display window
 that provides a Real Time Spectrum Analyzer (RTSA)-like spectrum
 visualization using OpenCL and OpenGL acceleration.
 .
 To use the fosphor blocks in Python, import it as :
 .
 from gnuradio import fosphor
 .
 See the Doxygen documentation for details about the blocks available
 in this package. A quick listing of the details can be found in Python
 after importing by using:
 .
 help(fosphor)