std::rt::uv::net: Handle `read_start` error

cc #9605
std::rt: Add NotConnected to IoErrorKind
rt::io::net::tcp: Fix eof_twice tests on Win32

cc #8811
extra: implement Encodable/Decodable for Uuid
Allow stage0 warnings
uuid: serialize test and documentations
auto merge of #9721 : klutzy/rust/uv-net-read-fix, r=alexcrichton

See #9605 for detailed information.

This also fixes two tests of #8811.
Added comments to public functions in num.rs.

Copied existing comments from other files, and added comments to
functions that did not have existing comments available.
auto merge of #9585 : vky/rust/num-docs, r=alexcrichton

Copied existing comments from other files, and added comments to functions that did not have existing comments available. 

cc #7511
Removed the -Z once_fns compiler flag and added the new feature directive of the same name to replace it.
Changed the frame_address intrinsic to no longer be a once fn.
This removes the dependency on once_fns from std.
auto merge of #9846 : cmr/rust/serialize_uuid, r=alexcrichton
Fixed example comment for num::cast().
auto merge of #9891 : alexcrichton/rust/allow-warnings, r=brson

Closes #9754
Rewrite vec.contains() to be simpler
Implement new methods vec.starts_with()/vec.ends_with()
Rewrite str.starts_with()/ends_with() to be simpler
auto merge of #9863 : csainty/rust/issue-9755-once-fns-feature-directive, r=alexcrichton

Hello,

First time rust contributor here, please let me know if I need to sort out the contribution agreement for this.

I picked issue #9755 to dip my toe in the water, this pull request isn't quite complete though as I have not updated the documentation. The reason for this is that I haven't tracked down why this feature is gated so I don't feel I can write a justification of the same quality as the other features have been documented.
If someone would like to explain or point me at a mail thread I am happy to update with this change.

Hopefully I have understood the process of converting the old flag into a directive correctly.

Also just to call out what I am sure if a known quirk when adding feature directives, you can't build this code unless you have a snapshot of the compiler which knows about the feature directive. Chicken and the egg. I split the change into two commits, the first should be able to build a snapshot that can compile the second.
auto merge of #9897 : thestinger/rust/rusti, r=alexcrichton

Closes #9818
Closes #9567
Closes #8924
Closes #8910
Closes #8392
Closes #7692
Closes #7499
Closes #7220
Closes #5038
auto merge of #9900 : hatahet/rust/master, r=alexcrichton

Closes #9870
auto merge of #9907 : kballard/rust/vec_ends_with, r=alexcrichton