Configuration Menu System support for external OSD

A quick hack to support config menu on external OSD, consisiting of:

- CMS-OSD partial separation (CMS and OSD reside in a same file: osd.c)
- MSP message injection (take it as server-push in client-server model)

src/main/main.c

@@ -127,6 +127,14 @@ extern uint8_t motorControlEnable;
 serialPort_t *loopbackPort;
 #endif
 
+#ifdef USE_DPRINTF
+#include "common/printf.h"
+#define DPRINTF_SERIAL_PORT SERIAL_PORT_USART3
+serialPort_t *debugSerialPort = NULL;
+#define dprintf(x) if (debugSerialPort) printf x
+#else
+#define dprintf(x)
+#endif
 
 typedef enum {
     SYSTEM_STATE_INITIALISING   = 0,
@@ -245,6 +253,16 @@ void init(void)
     serialInit(&masterConfig.serialConfig, feature(FEATURE_SOFTSERIAL), SERIAL_PORT_NONE);
 #endif
 
+#ifdef USE_DPRINTF
+    // Setup debugSerialPort
+
+    debugSerialPort = openSerialPort(DPRINTF_SERIAL_PORT, FUNCTION_NONE, NULL, 115200, MODE_RXTX, 0);
+    if (debugSerialPort) {
+        setPrintfSerialPort(debugSerialPort);
+        dprintf(("debugSerialPort: OK\r\n"));
+    }
+#endif
+
     mixerInit(masterConfig.mixerMode, masterConfig.customMotorMixer);
 #ifdef USE_SERVOS
     servoMixerInit(masterConfig.customServoMixer);