Added preliminary MPU-401 emulation (UART mode only) for SB16. Currently outputs to default Windows MIDI device. This allows Windows 3.x SB16 drivers to work.

src/sound_mpu401_uart.h

@@ -0,0 +1,9 @@
+typedef struct mpu401_uart_t
+{
+        uint8_t status;
+        uint8_t rx_data;
+
+        int uart_mode;        
+} mpu401_uart_t;
+
+void mpu401_uart_init(mpu401_uart_t *mpu, uint16_t addr);