4Store (1.1.4) compliance

- `4Store` (1.1.4) compliance
- Replace curl_* operations with the appropriate $httpRequest operation
- `4Store` encoding issue has been pointed out by Dbeeson in [gerrit70047][70047]

### Test environment

The following settings have been used to run all tests and ` php rebuildData.php -v` against `4Store` v1.1.4-2
```
4s-httpd -p 8088 smw
$smwgSparqlDatabaseConnector = '4store';
$smwgSparqlQueryEndpoint = 'http://localhost:8088/sparql/';
$smwgSparqlUpdateEndpoint = 'http://localhost:8088/update/';
$smwgSparqlDataEndpoint = 'http://localhost:8088/data/';
$smwgSparqlDefaultGraph = 'http://example.org/mydefaultgraphname';
```
### Bugs to be solved

- https://bugzilla.wikimedia.org/show_bug.cgi?id=43708
- https://bugzilla.wikimedia.org/show_bug.cgi?id=44700

### Test coverage changes
[Changes](https://scrutinizer-ci.com/g/SemanticMediaWiki/SemanticMediaWiki/inspections/99dd45d0-9408-452c-991a-ab81b905a549/code-structure/test-coverage)


[70047]: https://gerrit.wikimedia.org/r/#/c/70047/4/includes/sparql/SMW_SparqlDatabase4Store.php