Extend the parser grammer to allow labels before or after any
property data (string, cell list, or byte list), and any
byte or cell within the property data.
Store the labels using the same linked list structure as node
references, but using a parallel list.
When writing assembly output emit global labels as offsets from
the start of the definition of the data.
Note that the alignment for a cell list is done as part of the
opening < delimiter, not the = or , before it. To label a cell
after a string or byte list put the label inside the cell list.
For example,
prop = zero: [ aa bb ], two: < four: 1234 > eight: ;
will produce labels with offsets 0, 2, 4, and 8 bytes from
the beginning of the data for property prop.
Signed-off-by: Milton Miller <miltonm@bga.com>