Tighten up float literal lexing.

Specifically, dissallow setting the number base for every type of float
literal, not only those that contain the decimal point. This is in line with
the description in the manual.
Add /doc/rustuv to .gitignore
auto merge of #11480 : SiegeLord/rust/float_base, r=cmr

This fixes the incorrect lexing of things like:

~~~rust
let b = 0o2f32;
let d = 0o4e6;
let f = 0o6e6f32;
~~~

and brings the float literal lexer in line with the description of the float literals in the manual.
auto merge of #11483 : kballard/rust/gitignore-doc-rustuv, r=alexcrichton
doc: build the docs for librustpkg
Restore missing line breaks in doc/index.html

a30d61b05a removed all of the trailing whitespace in doc/index.md.
Unfortunately, that trailing whitespace was actually markdown syntax for
line breaks.
Add librustuv to doc/index.md
Add inline attributes documentation.

Closes #7959.
auto merge of #11488 : kballard/rust/librustpkg-docs, r=brson
auto merge of #11491 : wting/rust/wting_7959_document_inline_attributes, r=alexcrichton

Closes #7959.
more backticks
auto merge of #11495 : kud1ing/rust/backticks, r=huonw
Don't overwrite the options.output value from build_session_options