change chan osc range - PLEASE READ

as of now the range is ~32768, either from -16384 to 16383, or 0 to 32767.
it previously was -32768 to 32767 (~65536).

this change was made to better suit chips that only output a positive value.
if you are working on a new chip, update your code and shift right by one if necessary.

src/engine/platform/ga20.cpp

@@ -75,7 +75,7 @@ void DivPlatformGA20::acquire(short** buf, size_t len) {
     ga20.sound_stream_update(buffer, 1);
     buf[0][h]=(signed int)(ga20Buf[0][h]+ga20Buf[1][h]+ga20Buf[2][h]+ga20Buf[3][h])>>2;
     for (int i=0; i<4; i++) {
-      oscBuf[i]->data[oscBuf[i]->needle++]=ga20Buf[i][h];
+      oscBuf[i]->data[oscBuf[i]->needle++]=ga20Buf[i][h]>>1;
     }
   }
 }