Command is now an enum
Move syslog to BuildContext
Move command line parsing to parse_args.rs
Fix some of the testcases
simple-lib and deeply and c-dependencies still have problems.
But they were nt caused by this pull request
Use ~-objects instead of @-objects for syntax exts

This is necessary for #11151 to make sure dtors run before the libraries
are unloaded.
Remove a fixme

I don't think it's relevant, a warning is more appropriate. Easier to just
maintain the order.

Closes #4681
Add tidy support for snapshots

This let's us specify exactly which snapshot a given note to update after
snapshot is for.

Closes #2483
Remove a fixme

pcwalton says this is right, and it looks right to me too.

Closes #4731
tidy: spew less chaff
std: mark some modules as unstable

Obviously everything is unstable, but these particularly so, and they will
likely remain that way.

Closes #10239
Fix some warnings
Don't wait for a full buffer when reading TCP

libnative erroneously would attempt to fill the entire buffer in a call to
`read` before returning, when rather it should return immediately because
there's not guaranteed to be any data that will ever be received again.

Close #11328
auto merge of #11327 : nielsle/rust/rustpkg_argparse, r=alexcrichton

Rearrange some code in rustpkg:

* Move command line argument parsing to  parse_args.rs
* Introduce an enum to descibe commands such as Build, Install, and Clean.
* Move sysroot from Context to BuildContext, to make parse_args  more modular.

This is my first pull request, so please tell me if there is anything I need to do.
auto merge of #11332 : sfackler/rust/de-at-se, r=huonw

This is necessary for #11151 to make sure dtors run before the libraries
are unloaded.
auto merge of #11333 : cmr/rust/triage2, r=alexcrichton
auto merge of #11334 : alexcrichton/rust/fix-native-tcp, r=pcwalton

libnative erroneously would attempt to fill the entire buffer in a call to
`read` before returning, when rather it should return immediately because
there's not guaranteed to be any data that will ever be received again.

Close #11328
Use target libraries instead of host libraries. Fixes #11243
Don't attempt duplicate outputs

This ends up causing weird errors like those seen in #11346

Closes #11346
wip