A subset of the original v4 patch (which will become v5 eventually)

The main operational difference is that for v4 effect onward, the 
sound name will now be *TRACK*.  This will not affect existing
effects since they use version number 3 or less.

This also provides the Nyquist effect with much more information about
the current processing:

Variable       Property    What
*AUDACITY*     VERSION     current Audacity version number

*SYSTEM-DIR*   BASE        Audacity install path
*SYSTEM-DIR*   DATA        Audacity data path
*SYSTEM-DIR*   HELP        Audacity help path
*SYSTEM-DIR*   TEMP        Audacity temp file path
*SYSTEM-DIR*   PLUGIN      Audacity search path for Nyquist plugins

*PROJECT*      RATE        current project sample rate
*PROJECT*      TRACKS      total number of tracks in the project
*PROJECT*      WAVETRACKS  number of wave tracks in the project
*PROJECT*      LABELTRACKS number of label tracks in the project
*PROJECT*      MIDITRACKS  number of midi tracks in the project
*PROJECT*      TIMETRACKS  number of time tracks in the project

*SELECTION*    START       start time of current selection
*SELECTION*    END         end time of current selection
*SELECTION*    TRACKS      number of tracks in the current selection
*SELECTION*    CHANNELS    number of channels in the current selection
*SELECTION*    LOW-HZ      low frequency from spectrogram (if available, else nil)
*SELECTION*    CENTER-HZ   center frequence (calculated) (if available, else nil)
*SELECTION*    HIGH-HZ     high frequence from spectrogram (if available, else nil)
*SELECTION*    BANDWIDTH   bandwidth in octaves (calculated) (if available, else nil)
*SELECTION*    PEAK-LEVEL  peak amplitude for the current selection

*TRACK*        INDEX       1-based index of track being processed
*TRACK*        NAME        name of track
*TRACK*        TYPE        type of track: wave, midi, label, time
*TRACK*        VIEW        track view: Waveform,  Waveform (dB), etc.
*TRACK*        CHANNELS    number of channels in the track
*TRACK*        START-TIME  start time of track
*TRACK*        END-TIME    end time of track
*TRACK*        GAIN        track gain
*TRACK*        PAN         track pan
*TRACK*        RATE        sample rate of track
*TRACK*        FORMAT      sample format: 16 (int), 24 (int), 32.0 (float)
*TRACK*        CLIPS       list of start/end times for clips for each channel

lib-src/libnyquist/nyx.h

@@ -61,6 +61,9 @@ extern "C"
                                    void *userdata,
                                    int num_channels,
                                    long len, double rate);
+
+   char       *nyx_get_audio_name();
+   void        nyx_set_audio_name(const char *name);
    
    nyx_rval    nyx_eval_expression(const char *expr);