chore(fmod): add files from Chensne/DragonNest

lib/freeverb/allpass.cpp

@@ -0,0 +1,36 @@
+// Allpass filter implementation
+//
+// Written by Jezar at Dreampoint, June 2000
+// http://www.dreampoint.co.uk
+// This code is public domain
+
+#include "allpass.h"
+
+allpass::allpass()
+{
+	bufidx = 0;
+}
+
+void allpass::setbuffer(float *buf, int size) 
+{
+	buffer = buf; 
+	bufsize = size;
+}
+
+void allpass::mute()
+{
+	for (int i=0; i<bufsize; i++)
+		buffer[i]=0;
+}
+
+void allpass::setfeedback(float val) 
+{
+	feedback = val;
+}
+
+float allpass::getfeedback() 
+{
+	return feedback;
+}
+
+//ends