ZynAddSubFX: allocate spectrum on heap instead of stack

When loading some presets the PADnoteParameters spectrum size is 524288
or even bigger resulting in a stack allocation of 2 MB or more.
This results in a stack overflow on Win32 and thus crashes LMMS. Fix this
by allocating the spectrum on the heap instead.

Closes #543.

plugins/zynaddsubfx/src/Params/PADnoteParameters.cpp

@@ -555,7 +555,7 @@ void PADnoteParameters::applyparameters(bool lockmutex)
 {
     const int samplesize   = (((int) 1) << (Pquality.samplesize + 14));
     int      spectrumsize = samplesize / 2;
-    REALTYPE spectrum[spectrumsize];
+    REALTYPE *spectrum = new REALTYPE[spectrumsize];
     int      profilesize  = 512;
     REALTYPE profile[profilesize];
 
@@ -653,6 +653,8 @@ void PADnoteParameters::applyparameters(bool lockmutex)
     delete (fft);
     deleteFFTFREQS(&fftfreqs);
 
+	delete[] spectrum;
+
     //delete the additional samples that might exists and are not useful
     if(lockmutex) {
         pthread_mutex_lock(mutex);