Complete and fix defines for various boards

This adds relevant defines that identify the architecture and board
currently compiled for. Most of these are usually set by the platform's
platform.txt and boards.txt, except for the __AVR* defines that are set
by avr-gcc internally.

This only adds extra defines, except for the Arduino Due, which
previously incorrectly identified as an ATmega328p.

This seems to fix part of Arduino-CI#89.

Author: matthijskooijman

Diff for: misc/default.yml

@@ -22,7 +22,10 @@ platforms:
     gcc:
       features:
       defines:
+        - __AVR__
         - __AVR_ATmega328P__
+        - ARDUINO_ARCH_AVR
+        - ARDUINO_AVR_UNO
       warnings:
       flags:
   due:
@@ -31,7 +34,9 @@ platforms:
     gcc:
       features:
       defines:
-        - __AVR_ATmega328__
+        - __SAM3X8E__
+        - ARDUINO_ARCH_SAM
+        - ARDUINO_SAM_DUE
       warnings:
       flags:
   zero:
@@ -40,8 +45,9 @@ platforms:
     gcc:
       features:
       defines:
-       - __SAMD21G18A__
-       - ARDUINO_SAMD_ZERO
+        - __SAMD21G18A__
+        - ARDUINO_ARCH_SAMD
+        - ARDUINO_SAMD_ZERO
       warnings:
       flags:
   esp32:
@@ -50,6 +56,9 @@ platforms:
     gcc:
       features:
       defines:
+        - ESP32
+        - ARDUINO_ARCH_ESP32
+        - ARDUINO_FEATHER_ESP32
       warnings:
       flags:
   esp8266:
@@ -58,6 +67,9 @@ platforms:
     gcc:
       features:
       defines:
+        - ESP8266
+        - ARDUINO_ARCH_ESP8266
+        - ARDUINO_ESP8266_ESP12
       warnings:
       flags:
   leonardo:
@@ -66,7 +78,10 @@ platforms:
     gcc:
       features:
       defines:
+        - __AVR__
         - __AVR_ATmega32U4__
+        - ARDUINO_ARCH_AVR
+        - ARDUINO_AVR_LEONARDO
       warnings:
       flags:
   trinket:
@@ -75,6 +90,10 @@ platforms:
     gcc:
       features:
       defines:
+        - __AVR__
+        - __AVR_ATtiny85__
+        - ARDUINO_ARCH_AVR
+        - ARDUINO_AVR_TRINKET5
       warnings:
       flags:
   gemma:
@@ -83,6 +102,10 @@ platforms:
     gcc:
       features:
       defines:
+        - __AVR__
+        - __AVR_ATtiny85__
+        - ARDUINO_ARCH_AVR
+        - ARDUINO_AVR_GEMMA
       warnings:
       flags:
   m4:
@@ -91,6 +114,10 @@ platforms:
     gcc:
       features:
       defines:
+        - __SAMD51__
+        - __SAMD51J19A__
+        - ARDUINO_ARCH_SAMD
+        - ARDUINO_METRO_M4
       warnings:
       flags:
   mega2560:
@@ -99,7 +126,10 @@ platforms:
     gcc:
       features:
       defines:
+        - __AVR__
         - __AVR_ATmega2560__
+        - ARDUINO_ARCH_AVR
+        - ARDUINO_AVR_MEGA2560
       warnings:
       flags:
   cplayClassic:
@@ -108,6 +138,10 @@ platforms:
     gcc:
       features:
       defines:
+        - __AVR__
+        - __AVR_ATmega32U4__
+        - ARDUINO_ARCH_AVR
+        - ARDUINO_AVR_CIRCUITPLAY
       warnings:
       flags:
   cplayExpress:
@@ -116,6 +150,9 @@ platforms:
     gcc:
       features:
       defines:
+        - __SAMD21G18A__
+        - ARDUINO_ARCH_SAMD
+        - ARDUINO_SAMD_CIRCUITPLAYGROUND_EXPRESS
       warnings:
       flags: