E.memoryArea not working on ESP8266 (due to char-iterator ?)

Maybe E.memoryArea should use flash addresses (starting at 0) instead of memory mapped addresses?

I guess we'd need some ESP8266-specific tweaks in there for that, but it could be a plan.

In any case, it can only access the first 1MB of flash due to esp8266 memory mapping limitations.

@Wilberforce So jshFlashRead could potentially use more memory as it can use API calls, but memoryArea needs a pointer, so it will never be able to access more than the first 1MB.