- update to 0.16.1:
* fixed a build issue on 32-bit linux platforms, caused by slicing of integer
string ID values.
* worked around floating point rounding errors which prevented two
theoretically-equal numeric values from being evaluated as equal in test
code.
* added new function to allow printing of single formula tokens.
* added method for setting cached results on formula cells in
model_context.
* changed the model_context design to ensure that all sheets are of the same
size.
* added an accessor method to formula_model_access interface (and implicitly
in model_context) that directly returns a string value from cell.
* added cell_access class for querying of cell states without knowing its
type ahead of time.
* added document class which provides a layer on top of model_context, to
abstract away the handling of formula calculations.
* deprecated model_context::erase_cell() in favor of empty_cell().
* added support for 3D references - references that contain multiple sheets.
* added support for the exponent (^) and concatenation (&) operators.
* fixed incorrect handling of range references containing whole columns such
as A:A.
* added support for unordered range references - range references whose
start row or column is greater than their end position counterparts, such
as A3:A1.
* fixed a bug that prevented nested formula functions from working properly.
* implemented Calc A1 style reference resolver.
* formula results now directly store the string values when the results are
of string type. They previously stored string ID values after interning
the original strings.