Add `extra::getopts::short_usage`

This complements `usage` by auto-generating a short one-liner summary
of the options.
etc/tidy: don't check SNAP against triple
etc: add missing license boilerplates
rustdoc: update deps
auto merge of #11989 : adridu59/rust/tidy, r=alexcrichton

Closes #11985
Closes #4533

@huonw, @alexcrichton
Make a double-write UDP test more robust

I have a hunch this just deadlocked the windows bots. Due to UDP being a lossy
protocol, I don't think we can guarantee that the server can receive both
packets, so just listen for one of them.
auto merge of #12054 : alexcrichton/rust/less-flaky-udp, r=brson

I have a hunch this just deadlocked the windows bots. Due to UDP being a lossy
protocol, I don't think we can guarantee that the server can receive both
packets, so just listen for one of them.
auto merge of #12001 : yuriks/rust/getopts-tweaks, r=brson

This complements `usage` by auto-generating a short one-liner summary
of the options.

(First timer here, be gentle... :)
Removed @self and @Trait.