Added LED_BUILTIN to pins_arduino.h
Added LED_BUILTIN to pins_arduino.h

LED_BUILTIN is missing from all chipKIT board variants. This change adds it to pins_arduino.h which should map the PIN_LED1 from each board variants Board_Defs.h file to LED_BUILTIN while still allowing it to be specifically defined in Board_Defs.h should someone decide that PIN_LED1 doesn't make sense for their particular board.
majenkotech/chipKIT-core,EmbeddedMan/chipKIT-core,adamwolf/chipKIT-core,pontech/chipKIT-core,pontech/chipKIT-core,EmbeddedMan/chipKIT-core,ricklon/chipKIT-core,EmbeddedMan/chipKIT-core,majenkotech/chipKIT-core,chipKIT32/chipkit-core,majenkotech/chipKIT-core,adamwolf/chipKIT-core,chipKIT32/chipkit-core,pontech/chipKIT-core,pontech/chipKIT-core,ricklon/chipKIT-core,EmbeddedMan/chipKIT-core,ricklon/chipKIT-core,majenkotech/chipKIT-core,adamwolf/chipKIT-core,majenkotech/chipKIT-core,adamwolf/chipKIT-core,ricklon/chipKIT-core,majenkotech/chipKIT-core,ricklon/chipKIT-core,EmbeddedMan/chipKIT-core,chipKIT32/chipkit-core,pontech/chipKIT-core,EmbeddedMan/chipKIT-core,chipKIT32/chipkit-core,majenkotech/chipKIT-core,ricklon/chipKIT-core,adamwolf/chipKIT-core,chipKIT32/chipkit-core,adamwolf/chipKIT-core,pontech/chipKIT-core,EmbeddedMan/chipKIT-core,pontech/chipKIT-core,adamwolf/chipKIT-core