Gqrx SDR 2.15

• Start/stop RDS and fetch Program Identification via remote control.
• Added IQ balancing to MacOS release.
• Fixed erratic behaviour of S-meter.
• Fixed compilation error due to missing include.
• Fixed startup crash on Windows.
• Fixed I/Q playback when filename contains special characters.
• Reordered the receiver mode drop-down list.
• Receiver mode is now stored as a string in settings files.
• Increased automatic squelch margin to 3 dB.