Add variable triangle waveform

examples/Synthesis/Waveforms/Waveforms.ino

         Serial.println("Triangle");
         break;
       case WAVEFORM_TRIANGLE:
+        current_waveform = WAVEFORM_TRIANGLE_VARIABLE;
+        Serial.println("Variable Triangle");
+        break;
+      case WAVEFORM_TRIANGLE_VARIABLE:
         current_waveform = WAVEFORM_ARBITRARY;
         Serial.println("Arbitary Waveform");
         break;

gui/index.html

 		<li><span class=literal>WAVEFORM_SAWTOOTH_REVERSE</span></li>
 		<li><span class=literal>WAVEFORM_SQUARE</span></li>
 		<li><span class=literal>WAVEFORM_TRIANGLE</span></li>
+		<li><span class=literal>WAVEFORM_TRIANGLE_VARIABLE</span></li>
 		<li><span class=literal>WAVEFORM_ARBITRARY</span></li>
 		<li><span class=literal>WAVEFORM_PULSE</span></li>
 		<li><span class=literal>WAVEFORM_SAMPLE_HOLD</span></li>

keywords.txt

 WAVEFORM_PULSE	LITERAL1
 WAVEFORM_SAWTOOTH_REVERSE	LITERAL1
 WAVEFORM_SAMPLE_HOLD	LITERAL1
+WAVEFORM_TRIANGLE_VARIABLE	LITERAL1
 
 AUDIO_MEMORY_23LC1024	LITERAL1
 AUDIO_MEMORY_MEMORYBOARD	LITERAL1

synth_waveform.cpp

 		}
 		break;
 
+	case WAVEFORM_TRIANGLE_VARIABLE:
+		do {
+		uint32_t rise = 0xFFFFFFFF / (pulse_width >> 16);
+		uint32_t fall = 0xFFFFFFFF / (0xFFFF - (pulse_width >> 16));
+		for (i=0; i < AUDIO_BLOCK_SAMPLES; i++) {
+			if (ph < pulse_width/2) {
+				uint32_t n = (ph >> 16) * rise;
+				*bp++ = ((n >> 16) * magnitude) >> 16;
+			} else if (ph < 0xFFFFFFFF - pulse_width/2) {
+				uint32_t n = 0x7FFFFFFF - (((ph - pulse_width/2) >> 16) * fall);
+				*bp++ = ((n >> 16) * magnitude) >> 16;
+			} else {
+				uint32_t n = ((ph + pulse_width/2) >> 16) * rise + 0x80000000;
+				*bp++ = ((n >> 16) * magnitude) >> 16;
+			}
+			ph += inc;
+		}
+		} while (0);
+		break;
+
 	case WAVEFORM_PULSE:
 		magnitude15 = signed_saturate_rshift(magnitude, 16, 1);
 		for (i=0; i < AUDIO_BLOCK_SAMPLES; i++) {

synth_waveform.h

 }
 
 
-#define WAVEFORM_SINE      0
-#define WAVEFORM_SAWTOOTH  1
-#define WAVEFORM_SQUARE    2
-#define WAVEFORM_TRIANGLE  3
-#define WAVEFORM_ARBITRARY 4
-#define WAVEFORM_PULSE     5
-#define WAVEFORM_SAWTOOTH_REVERSE 6
-#define WAVEFORM_SAMPLE_HOLD 7
-
+#define WAVEFORM_SINE              0
+#define WAVEFORM_SAWTOOTH          1
+#define WAVEFORM_SQUARE            2
+#define WAVEFORM_TRIANGLE          3
+#define WAVEFORM_ARBITRARY         4
+#define WAVEFORM_PULSE             5
+#define WAVEFORM_SAWTOOTH_REVERSE  6
+#define WAVEFORM_SAMPLE_HOLD       7
+#define WAVEFORM_TRIANGLE_VARIABLE 8
 
 class AudioSynthWaveform : public AudioStream
 {