* Allow GPIO 9 and 10 for waveform generation
While most ESP8266 modules use quad-io mode for their SPI flash ROM,
there are some which only use dual-io mode. Allow the unused pins
(GPIO 9 and 10) to have waveforms generated on them. Should the user try
this on a quad-io mode board, expect very bad things to happen.
* Add variant for 8285 to init GPIO 9/10
The 8285 only has 2-bit flash IO, so the other two pins can be used as
inputs (9/10). Set them to input to mirror the way other pins are set
up.
* Update waveform gen to only allow 9/10 on 8285
Update the common.h in both generic (remove TODO, it's done!) and the
8285 variant to make isFlashInterfacePin macro correct. Use that macro
to disable pins 9 and 10 in the common, non-8285 case.
* LED_BUILTIN should be a #define
deduplicate and hide BUILTIN_LED as a deprecated constant
* test for LED_BUILTIN existence
* board:espino:variant: rename button macro (naming coherence)
