Read vibrato waveform type

test/testdata.js

@@ -25,6 +25,7 @@ exports.resetXMData = function() {
     vibratopos: 0,
     vibratodepth: 1,
     vibratospeed: 1,
+    vibratotype: 0,
   });
   xm.songpats = [0];
   // 1 channel, 2 row blank pattern

xm.js

@@ -697,6 +697,7 @@ function load(arrayBuf) {
       vibratopos: 0,
       vibratodepth: 1,
       vibratospeed: 1,
+      vibratotype: 0,
     });
   }
   console.log("header len " + hlen);

xmeffects.js

@@ -135,6 +135,9 @@ function eff_t0_e(ch, data) {  // extended effects!
     case 2:  // fine porta down
       ch.period += data;
       break;
+    case 4:  // set vibrato waveform
+      ch.vibratotype = data & 0x07;
+      break;
     case 5:  // finetune
       ch.fine = (data<<4) + data - 128;
       break;