Implement macro definitions

[craigthomas]

A macro is a block of assembly language statements that can be defined and then inserted into an assembly language program at any location. A macro is defined by a MACRO and then ENDM pair. A macro must also have a label. The macro is called within the assembly language routine by using the symbol name as if it were any other mnemonic. Values can be passed to macros within the operand field when specifying the macro. Passed values are specified within the macro definition with the \ character and the number for the value (the first passed value will be \0, the next \1, etc). For example:

TEST    MACRO
        LDA \0
        ENDM

        ORG $0E00
        TEST #$40
        END

Macros cannot be nested.