STRUCTURE <start label>,<offset> ; => <start label> EQU <offset>
FPTR/APTR/BPTR <label> ; => new label, advance offset by 4
BYTE/UBTYE <label> ; => advance by 1
WORD/UWORD/SHORT/USHORT <label> ; => advance by 2
BOOL <label> ; advance by 2
LONG/ULONG <label> ; => advance by 4
FLOAT/DOUBLE <label> ; => advance by 4
LABEL <label> ; => get current offset, great for _SIZEOF
STRUCT <label>,<size> ; => advance by <size>
ALIGNWORD/ALIGNLONG ; change offset to be word/long aligned

; ENUMs always start at 0. get rid of those magic numbers!
ENUM <name> ; => start a new enum, can only define once!
EITEM <name> ; => <name> EQU enum offset, add 1 to offset

; BITDEF makes two EQUs
BITDEF <prefix>,<identifier>,<bit>
; => <prefix>B_<identifier> EQU <bit>
; => <prefix>F_<identifier> EQU 1<<<bit>