initial commit

took me a day to make the base...
...and ~12 hours to write a reader that reads 100% of all demo songs in
1.0

src/engine/pattern.h

@@ -0,0 +1,15 @@
+struct DivPattern {
+  char data[256][16];
+};
+
+struct DivChannelData {
+  char effectRows;
+  // data goes as follows: data[ROW][TYPE]
+  // TYPE is:
+  // 0: note
+  // 1: octave
+  // 2: instrument
+  // 3: volume
+  // 4-5+: effect/effect value
+  std::vector<DivPattern*> data;
+};