Highlight reserved hardware labels

I along with other users would find it helpful for the Arduino IDE to automatically colour reserved hardware labels (registers and bits, each with a different colour) for each selectable microcontroller type along with analog pins (e.g. A0, A1 etc.)

Start in the Arduino IDE's editor syntax-highlighting implementation and inspect how selectable microcontroller types are represented. Determine how registers, bits, and analog pins such as A0 and A1 are defined for each type. Done means reserved hardware labels are automatically highlighted with separate colors for registers, bits, and analog pins.

Written by the indexing model from the issue text.