Added Serial line encoding functions + events

arduino/Arduino#2469
Weak implementation sounds usefull but takes 6 more bytes of flash/
function (12). Even more, if we would also pass the line states but the
user can read this with Serial.dtr() for example.

arduino/Arduino#1179
Should we inline the Serial.dtr() functuions etc? But then we need to
move the line info to the header as well, also the definition.
These optional functions only take flash if they are used. Virtual isnt
used, because this would take more flash for no reason.
Syntax like this: https://www.pjrc.com/teensy/td_serial.html

Author: Nico

plugins/KeyboardioHID/CDC.cpp

@@ -80,11 +80,13 @@ bool WEAK CDC_Setup(Setup& setup)
 		if (CDC_SET_LINE_CODING == r)
 		{
 			USB_RecvControl((void*)&_usbLineInfo, 7);
+			CDC_LineEncodingEvent();
 		}
 
 		if (CDC_SET_CONTROL_LINE_STATE == r)
 		{
 			_usbLineInfo.lineState = setup.wValueL;
+			CDC_LineStateEvent();
 		}
 
 		if (CDC_SET_LINE_CODING == r || CDC_SET_CONTROL_LINE_STATE == r)
@@ -146,6 +148,15 @@ bool WEAK CDC_Setup(Setup& setup)
 	return false;
 }
 
+void WEAK CDC_LineEncodingEvent(void)
+{
+	// has to be implemented by the user
+}
+
+void WEAK CDC_LineStateEvent(void)
+{
+	// has to be implemented by the user
+}
 
 void Serial_::begin(unsigned long /* baud_count */)
 {
@@ -221,6 +232,36 @@ size_t Serial_::write(const uint8_t *buffer, size_t size)
 	return 0;
 }
 
+uint32_t Serial_::baud(void)
+{
+	return _usbLineInfo.dwDTERate;
+}
+
+uint8_t Serial_::stopbits(void)
+{
+	return _usbLineInfo.bCharFormat;
+}
+
+uint8_t Serial_::paritytype(void)
+{
+	return _usbLineInfo.bParityType;
+}
+
+uint8_t Serial_::numbits(void)
+{
+	return _usbLineInfo.bDataBits;
+}
+
+bool Serial_::dtr(void)
+{
+	return (_usbLineInfo.lineState & CDC_CONTROL_LINE_OUT_DTR) ? true : false;
+}
+
+bool Serial_::rts(void)
+{
+	return (_usbLineInfo.lineState & CDC_CONTROL_LINE_OUT_RTS) ? true : false;
+}
+
 // This operator is a convenient way for a sketch to check whether the
 // port has actually been configured and opened by the host (as opposed
 // to just being connected to the host).  It can be used, for example, in 

plugins/KeyboardioHID/HID_Tests/HID_Tests.ino

@@ -0,0 +1,35 @@
+// simply, ugly code to test the new functions
+
+void setup() {
+  Serial.begin(1);
+}
+
+uint32_t eventBaud = 0;
+
+void loop() {
+  if (Serial.available()) {
+    while (Serial.read() != -1);
+    Serial.println("Serial Port working");
+    Keyboard.println("Nico is cool");
+    delay(3000);
+  }
+
+  delay(3000);
+  Serial.println(Serial.dtr());
+  Serial.println(Serial.rts());
+  Serial.println(Serial.baud());
+  Serial.println(Serial.stopbits());
+  Serial.println(Serial.paritytype());
+  Serial.println(Serial.numbits());
+
+  if (eventBaud) {
+    Serial.println("Event");
+    Serial.println(eventBaud);
+    eventBaud = 0;
+  }
+}
+
+void CDC_LineEncodingEvent(void)
+{
+  eventBaud = Serial.baud();
+}

plugins/KeyboardioHID/USBAPI.h

@@ -82,6 +82,12 @@ class Serial_ : public Stream
 	virtual size_t write(uint8_t);
 	virtual size_t write(const uint8_t*, size_t);
 	using Print::write; // pull in write(str) and write(buf, size) from Print
+	uint32_t baud(void);
+	uint8_t stopbits(void);
+	uint8_t paritytype(void);
+	uint8_t numbits(void);
+	bool dtr(void);
+	bool rts(void);
 	operator bool();
 
 	volatile uint8_t _rx_buffer_head;
@@ -222,6 +228,8 @@ bool	MSC_Data(uint8_t rx, uint8_t tx);
 int		CDC_GetInterface(uint8_t* interfaceNum);
 int		CDC_GetDescriptor(int i);
 bool	CDC_Setup(Setup& setup);
+void CDC_LineEncodingEvent(void);
+void CDC_LineStateEvent(void);
 
 //================================================================================
 //================================================================================

plugins/KeyboardioHID/USBCore.h

@@ -56,6 +56,9 @@
 #define CDC_GET_LINE_CODING			0x21
 #define CDC_SET_CONTROL_LINE_STATE	0x22
 
+#define CDC_CONTROL_LINE_OUT_DTR   (1 << 0)
+#define CDC_CONTROL_LINE_OUT_RTS   (1 << 1)
+
 #define MSC_RESET					0xFF
 #define MSC_GET_MAX_LUN				0xFE