Merge branch 'ht/doc' into next
* ht/doc:
Only minor changes.
Minor fixes.
Tiny change in text.
Mainly work related to documentation of arrowheads.
Documentation of 3D view model.
Comparing with HUGE_LENGTH instead of using isinf to detect infinite viewing distance.
Documentation relating to SingleList and ConsPair lists.
Documentation for meetpaths and applications in the linkpaths extension.
Adding --log-globals command line option.
Documentation of approximator and intersection.
Fixed bug in computation of path intersections.
Documentation for maximization along paths.
Adding object files to the ignore lists.
Added note on how to type the degree sign.
Renaming some functions on paths.