Modernize ';nyquist plug-in' header command.

Ref. QA topic: http://sourceforge.net/p/audacity/mailman/message/33193296/

plug-ins/SpectralEditMulti.ny

@@ -1,4 +1,4 @@
-;nyquist plug-in
+;nyquist plugin
 ;version 4
 ;type process
 ;name "Spectral edit multi tool"

plug-ins/SpectralEditParametricEQ.ny

@@ -1,4 +1,4 @@
-;nyquist plug-in
+;nyquist plugin
 ;version 4
 ;type process
 ;preview enabled

plug-ins/SpectralEditShelves.ny

@@ -1,4 +1,4 @@
-;nyquist plug-in
+;nyquist plugin
 ;version 4
 ;type process
 ;preview enabled

plug-ins/crossfadetracks.ny

@@ -1,4 +1,4 @@
-;nyquist plug-in
+;nyquist plugin
 ;version 4
 ;type process
 ;name "Crossfade Tracks..."

src/effects/nyquist/Nyquist.cpp

@@ -1231,7 +1231,10 @@ void EffectNyquist::Parse(wxString line)
       return;
    }
 
-   if (len == 2 && tokens[0] == wxT("nyquist") && tokens[1] == wxT("plug-in")) {
+   // As of version 4 plugins ";nyquist plug-in" is depricated in favour of ";nyquist plugin".
+   // The hyphenated version must be maintained while we support plugin versions < 4.
+   if (len == 2 && tokens[0] == wxT("nyquist") &&
+      (tokens[1] == wxT("plugin") || tokens[1] == wxT("plug-in"))) {
       mOK = true;
       return;
    }