Add a complete example of the buffer mod for arduino

Documentation/Laser/README.md

@@ -10,3 +10,52 @@ mega256.build.extra_flags=-DSERIAL_RX_BUFFER_SIZE=256 -DSERIAL_TX_BUFFER_SIZE=25
 
 and then in the arduino ide select "mega 2560 serial buffer 256" board.
 
+
+In my boards.txt mega256 appears as this:
+
+```
+##############################################################
+mega256.name=Arduino/Genuino Mega or Mega 2560 256 serialbuf
+
+mega256.vid.0=0x2341
+mega256.pid.0=0x0010
+mega256.vid.1=0x2341
+mega256.pid.1=0x0042
+mega256.vid.2=0x2A03
+mega256.pid.2=0x0010
+mega256.vid.3=0x2A03
+mega256.pid.3=0x0042
+mega256.vid.4=0x2341
+mega256.pid.4=0x0210
+mega256.vid.5=0x2341
+mega256.pid.5=0x0242
+
+mega256.upload.tool=avrdude
+mega256.upload.maximum_data_size=8192
+
+mega256.bootloader.tool=avrdude
+mega256.bootloader.low_fuses=0xFF
+mega256.bootloader.unlock_bits=0x3F
+mega256.bootloader.lock_bits=0x0F
+
+mega256.build.f_cpu=16000000L
+mega256.build.core=arduino_256
+mega256.build.variant=mega
+# default board may be overridden by the cpu menu
+mega256.build.board=AVR_MEGA2560
+
+## Arduino/Genuino Mega w/ ATmega2560
+## -------------------------
+mega256.menu.cpu.atmega2560=ATmega2560 (Mega 2560)
+
+mega256.menu.cpu.atmega2560.upload.protocol=wiring
+mega256.menu.cpu.atmega2560.upload.maximum_size=253952
+mega256.menu.cpu.atmega2560.upload.speed=115200
+
+mega256.menu.cpu.atmega2560.bootloader.high_fuses=0xD8
+mega256.menu.cpu.atmega2560.bootloader.extended_fuses=0xFD
+mega256.menu.cpu.atmega2560.bootloader.file=stk500v2/stk500boot_v2_mega2560.hex
+
+mega256.menu.cpu.atmega2560.build.mcu=atmega2560
+mega256.menu.cpu.atmega2560.build.board=AVR_MEGA2560
+```