As mentioned in #9456, the format! syntax extension would previously consider an
empty format as a 'Unknown' format which could then also get coerced into a
different style of format on another argument.
This is unusual behavior because `{}` is a very common format and if you have
`{0} {0:?}` you wouldn't expect them both to be coereced to the `Poly`
formatter. This commit removes this coercion, but still retains the requirement
that each argument has exactly one format specified for it (an empty format now
counts as well).
Perhaps at a later date we can add support for multiple formats of one argument,
but this puts us in at least a backwards-compatible situation if we decide to do
that.
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.
