Headings with the exact same name generated exactly the same heading
names, which was invalid. This replaces the old code for generating
names for non-English headings which were using URI encode and resulted
in unreadable headings.
* FIX: Use theme color for anchor icon
* FIX: Do not count anchor links
* FIX: Do not count hashtags links either
* DEV: Add tests for link_count
* FIX: Disable anchors in quotes and preview
* FIX: Try building some anchor slugs for unicode
* DEV: Fix tests
