Support new source location fields in Python 3.8+

[Technologicat]

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Python 3.8 added the end_lineno and end_col_offset fields to AST nodes that have lineno and col_offset.

Specs in the official documentation.

We should probably worry about these anywhere we handle source location info.

[Technologicat]

Same in mcpyrate; tracked in https://github.com/Technologicat/mcpyrate/issues/32