rename writeBufferFree() to availableForWrite()

teensy3/HardwareSerial.h

 	virtual int read(void)          { return serial_getchar(); }
 	virtual void flush(void)        { serial_flush(); }
 	virtual void clear(void)	{ serial_clear(); }
-	virtual int writeBufferFree(void) { return serial_write_buffer_free(); }
+	virtual int availableForWrite(void) { return serial_write_buffer_free(); }
 	virtual size_t write(uint8_t c) { serial_putchar(c); return 1; }
 	virtual size_t write(unsigned long n)   { return write((uint8_t)n); }
 	virtual size_t write(long n)            { return write((uint8_t)n); }
 	virtual int read(void)          { return serial2_getchar(); }
 	virtual void flush(void)        { serial2_flush(); }
 	virtual void clear(void)	{ serial2_clear(); }
-	virtual int writeBufferFree(void) { return serial2_write_buffer_free(); }
+	virtual int availableForWrite(void) { return serial2_write_buffer_free(); }
 	virtual size_t write(uint8_t c) { serial2_putchar(c); return 1; }
 	virtual size_t write(unsigned long n)   { return write((uint8_t)n); }
 	virtual size_t write(long n)            { return write((uint8_t)n); }
 	virtual int read(void)          { return serial3_getchar(); }
 	virtual void flush(void)        { serial3_flush(); }
 	virtual void clear(void)	{ serial3_clear(); }
-	virtual int writeBufferFree(void) { return serial3_write_buffer_free(); }
+	virtual int availableForWrite(void) { return serial3_write_buffer_free(); }
 	virtual size_t write(uint8_t c) { serial3_putchar(c); return 1; }
 	virtual size_t write(unsigned long n)   { return write((uint8_t)n); }
 	virtual size_t write(long n)            { return write((uint8_t)n); }

teensy3/usb_seremu.h

         size_t write(long n) { return write((uint8_t)n); }
         size_t write(unsigned int n) { return write((uint8_t)n); }
         size_t write(int n) { return write((uint8_t)n); }
-	int writeBufferFree() { return usb_seremu_write_buffer_free(); }
+	int availableForWrite() { return usb_seremu_write_buffer_free(); }
 	using Print::write;
         void send_now(void) { usb_seremu_flush_output(); };
         uint32_t baud(void) { return 9600; }
 	size_t write(long n) { return 1; }
 	size_t write(unsigned int n) { return 1; }
 	size_t write(int n) { return 1; }
-	int writeBufferFree() { return 0; }
+	int availableForWrite() { return 0; }
 	using Print::write;
 	void send_now(void) { }
 	uint32_t baud(void) { return 0; }

teensy3/usb_serial.h

 	size_t write(long n) { return write((uint8_t)n); }
 	size_t write(unsigned int n) { return write((uint8_t)n); }
 	size_t write(int n) { return write((uint8_t)n); }
-	int writeBufferFree() { return usb_serial_write_buffer_free(); }
+	int availableForWrite() { return usb_serial_write_buffer_free(); }
 	using Print::write;
         void send_now(void) { usb_serial_flush_output(); }
         uint32_t baud(void) { return usb_cdc_line_coding[0]; }
 	size_t write(long n) { return 1; }
 	size_t write(unsigned int n) { return 1; }
 	size_t write(int n) { return 1; }
-	int writeBufferFree() { return 0; }
+	int availableForWrite() { return 0; }
 	using Print::write;
         void send_now(void) { }
         uint32_t baud(void) { return 0; }