When a key is pressed and held, this now does the OS-style repeating after a bit
of a pause. Also fixes the width of search results to be correct (was changed
beforehand and didn't catch this).
All items have source links back to their actual code. Source files can be
omitted with the doc(html_no_source) attribute on the crate. Currently there is
no syntax highlighting, but that will come with syntax highlighting with all
other snippets.
Closes#2072
Removes old rustdoc, moves rustdoc_ng into its place instead (plus drops the _ng
suffix). Also shreds all reference to rustdoc_ng from the Makefile rules.
