- Added patch:
* no-std-filesystem.patch
+ use boost::filesystem instead of std::filesystem, in order to
allow building with older compilers

- Update to 0.17.2:
* fixed a bug where the state of style:cell-protect="none" was not
explicitly pushed, thereby having had the same effect as not having this
attribute. After the fix, style:cell-protect="none" will explicitly push
the hidden state to false, locked state to false, and the formula-hidden
state to false.
- Update to 0.17.1:
* addressed a number of coverity issues.
* removed a variety of compiler warnings.
* re-generated sax parser tokens from ODF v1.3.
* revised the style import code to only push style attributes that are
actually specified in the XML.
* revised the XML structure validation strategy to ignore any mis-placed
elements and their sub structures rather than aborting the import.

- Update to 0.17.0:
* set the baseline C++ version to 17.
* cleaned up the public API to replace pstring with std::string_view, union
with std::variant, and boost::optional with std::optional. With this
change, the public API no longer has dependency on boost.
* switched to using ixion::model_iterator for horizontal iteration of cells
instead of using mdds::mtv::collection.
* fixed a bug where exporting a spreadsheet document containing adjacent
merged cells regions to html incorrectly exported the merged cell areas.
* cached cell values are now correctly loaded from the xlsx file.