[Feature request] Allow multiple labels per line

[Rangi42]

Based on leaderjord's question on Discord.

Now that Global: and .local labels are both column-independent, it should be possible to unambiguously lex and parse multiple labels per line. This would avoid surprise based on an implementation detail of the parser rules, and would allow use cases like these:

MyColor: MyColour: dw $7fff

ZeroFill:
    xor a
Fill: .loop
    ld [hli], a
    dec c
    jr nz, .loop
    ret

MyData: MyDataRow: my_data_macro "-"
    MyDataRowEnd:
    my_data_macro "A"
    my_data_macro "B"
    my_data_macro "C"
; data size is MyDataRowEnd - MyDataRow

[Rangi42]

Or even:

Fill: .loop: ld [hli], a :: dec c :: jr nz, .loop :: ret

:3