Add character values to Assembler v2

[gilkeidar]

Problem Description: Add character values to assembler (which are translated to their corresponding immediate values).

Example: Currently, to print a character to the display, one must know its exact character set value; for instance:

OUT #0x41, A    //    Print 'A' to the screen

This can be partially mended using Preprocessor constants:

.define 1 _A    0x41
OUT _A, A    //    Print 'A' to the screen

However, this requires one to define many constants if one wants to write arbitrary characters; instead, this should be a built-in feature of the Assembler, like so:

OUT 'A', A    //    Print 'A' to the screen

This should cover the entire character set of the ByteFrost display.