Merge further changes from EAPS `graphLib` for 5.0 release

[wbkboyer]

Continuing work from #37 and #46

Must merge EAPS graphLib updates into planarity/c/graphLib resulting from EAPS PR #217 and EAPS PR #221, and make sure all functions/methods are declared and defined in the correct order in:

• cgraphLib.pxd,
• cplanarity.pxd (no changes to planarity/classic/planarity.pyx needed),
• graphLib.pxd,
• graphLib.pyx,
• graph.pyx

Also, need to change order of g6_EndReached() in g6ReadIterationUtils.pyx, since this was left out of #50