Update low-level printf() function based on Minima/WiFi macros.

In case of Minima, it uses Serial.write(), otherwise (WiFi) Serial.print() which is better than Serial.write() + delay(2).

Fix an issue on UNO R4 Wifi.

Fixes an issue where characters are not output with continuous printf.

First release.

Fix an issue on UNO R4 WiFi.