- Added patch:
* libixion-boost-system.patch
+ fix missing symbols from boost_system library

- update to 0.17.0:
* set the baseline C++ version to 17.
* mdds has been internalized so that the public header no longer contains
references to mdds. With this change, the users can use different API
versions of mdds between the ixion build and run-time use.
* cleaned up public API to make use of std::string_view and std::variant
where appropriate.
* implemented built-in LEFT() function in the formula interpreter.
* it is no longer required to set the size of void* at build time to ensure
the binaries to be fully functional.
* fixed a bug where named expressions with names containing invalid
characters were still allowed in.