FM-Radio for C64

Requires a RDA5807SP FM-Radio chip to be connected to C64 User port as follows:

C64 UP Pin  Pin Name  RDA5807 Module pin
 1          GND       GND
 2          +5V       VCC
 C          PB0       DAT
 D          PB1       CLK

Not tested with other versions of RDA5807.

V.0.1 (15.4.2013) Timo V.
 - When program is started it tries to search for fmradio.cfg from disk.
   This configuration file does not exist initially but is generated if
   you store any channels to locations (1, 2, 3 ... 9, 0) and answer 'y'
   when exiting the program.
   Currently config file only supports stored channel data

 - Keyboard assignments:
  s - Toggle STEREO/MONO
  b - Toggle Bass Boost
  m - Toggle mute ON/OFF
  SPACE - Switch Radio ON / OFF
  : - Start scanning down
  ; - Start scanning up
  u - Increase freq by 100kHz
  d - Decrease freq by 100kHz
  + - Increase volume
  - - Decrease volume
  c - Channel store
  q - exit

 - If radio state is ON it is not switched OFF if you quit the program
