- update to 5.6.2:
* fix AST comparison
* fix handling of n-ary comparisons in AST
* fix symbolic atom iterator
* build wheels using cibuildwheel
* add support for parsing files in ASPIF format
* add theory related functions to backend
* add support for comparisons with more than one relation
* extend safety by computing intervals from comparisons
* add and ground base part by default in Python API
* remove experimental CSP extensions
* require at least MSVC 15.0 to build on Windows
* large code refactoring
* replace internal hash set implementation by external one
* fix `parse_files` in C++ API
* fix adding clauses during enumeration
* fix incremental projection with backend
* update to clasp version 3.3.8
* extend theory class to get version information
* improve performance of `Model.symbol`
* tidy up `clingo.hh` header regarding C++17 deprecations
* fix error handling while solving in Python API
* fix various outher bugs