Clingo

* extend theory class to get version information
* improve performance of `Model.symbol` (296)
* tidy up `clingo.hh` header regarding C++17 deprecations (344)
* fix error handling while solving in Python API (334)
* fix various outher bugs
* update to clasp version 3.3.7

* allow for using `not` as a theory operator (193)
* improve parsing of disjunctions (171)
* rename `max_size` to `size` in APIs and remove previous `size` method
(breaks backward compatibility but makes things consistent)
* refine cmake configuration variables (283)
(package maintainers might have to pay attention here)
* extend clingo API (236, 231, 228, 227, 187, 171, 174, 183)
* add type annotations and add stub files for type checkers (212)
* reimplement Python API using CFFI (253)
(breaks backward compatibility regarding the AST and some details)
* add `remove_watch` and `freeze_literal` to `propagate_init` (285)
* add support for Lua 5.4
* add options to select specific Lua/Python versions
* add single-shot solving option (269)
(see installation instructions)
* rename `clingo.Tuple` to `clingo.Tuple_`
(to avoid name clashes with `typing.Tuple`)
* fix propagator initialization (166)
* fix cleanup function and handling of theory (169)
* fix shifting of disjunctions (in clasp) (173)
* fix handling of pools in externals (179)
* fix logger in Python API (175)
* fix memory bugs regarding strings (196)
* fix undo function (191)
* fix adding literals in propagate init (192)
* fix handling of undefined arithmetics (218)
* fix incremental grounding (248)
* fix/improve handling of classical negation (268)
* update to clasp version 3.3.6 fixing various issues

* add extension to implement custom heuristics
* add const modifiers to C API
* add flags to external and const statements to match API functions
* fix python memleaks
* make compatible with msvc 15
* C ABI changes
* extended propagators
* C++ API changes
* unify usage of ProgramBuilder and Backend
* python API changes
* `TruthValue.{_True,_False}` becomes `TruthValue.{True_,False_}`
* `HeuristicType.{True,False}` becomes `TruthValue.{True_,False_}`
* `async` and yield becomes `async_` and `yield_`
* improve python API documentation
* use cmakes `find_python` module
* update to clasp version 3.3.5

* change C API to use numeric instead of symbolic literals
* affects assumptions and assigning/releasing externals
(breaks backward compatibility)
* added overloads to C++, python and lua API to support
both numeric and symbolic version
(preserves backward compatibility for most code)
* the python, C and C++ APIs now allow for customizing clingo by implementing
a custom main function but reusing the rest of the application including
the standard output
* add API function to detect conflicting programs
* add message logger to python and lua interface
* add support for primes in the beginning of identifiers and variable names
* add per solver registration of watches during propagator initialization
* add a directive to selectivel suppress undefined atom warnings
* add support for user defined statistics
* add _to_c functions for python API to be able to call C functions from
python
* only create ground representations for requested program parts when
grounding (71)
* improve program observer (19)
* support for binary, octal, and hexadecimal numbers (65)
* the backend has to be opened/closed now
* release python's GIL while grounding (82)
* TruthValue.{True,False} becomes TruthValue.{\_True,\_False} in python API
* improve API and it's documentation

* update to clasp version 3.3.4
* really fix --pre option
* fix link to potassco guide (74)
* fix location printing (78)
* fix linking problems (79)
* fix modulo zero (100)
* fix web builds (103)
* fix addding clauses after a model has been found (104)
* fix python program observer bindings (105)
* expose exponentiation operator in APIs
* improve python docstrings (101, 102)
* add option to build python and lua modules against an existing libclingo

* update to clasp version 3.3.3
* use GNUInstallDirs in cmake files to simplify packaging
* fix --pre option
* fix swapped clingo\_assignment\_size and clingo\_assignment\_max\_size
* fix docstrings
* fix incremental mode
* fix sup and inf in python/lua bindings
* fix reified format term tuples
* fix wrong use of python API (causing trouble with python 3.6)
* fix compilation problems on 32bit linux (missing libatomic)