This slurps up everything inside of an 'extern' block into the enclosing module
in order to document them. The documentation must be on the items themselves,
and they'll show up next to everything else on the module index pages.
Closes#5953
This will probably need to get tweaked once the privacy rules have been fully
agreed on, but for now this has all of the infrastructure necessary for
filtering out private items.
Closes#9410
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.
