Make the parser compliant with JSON5 specs

[aqrln]

Not compliant as in "strictly adhering to" but as in "must parse everything that JSON5 allows and probably beyond and must serialize to valid JSON5".

• [x] Native parser (https://github.com/metarhia/jstp/issues/175, https://github.com/metarhia/jstp/pull/201, https://github.com/metarhia/jstp/pull/207, https://github.com/metarhia/jstp/pull/208, https://github.com/metarhia/jstp/pull/218, https://github.com/metarhia/jstp/pull/219, https://github.com/metarhia/jstp/pull/221, https://github.com/metarhia/jstp/pull/223, https://github.com/metarhia/jstp/pull/239, https://github.com/metarhia/jstp/issues/247)
• [ ] JavaScript parser

[belochub]

@metarhia/jstp-core, I've updated the description to represent current progress on this issue.