[MacPorts] #45412: Update Rust to 0.12

[MacPorts]

#45412: Update Rust to 0.12
----------------------------+--------------------------------
 Reporter:  macports.org@…  |      Owner:  macports-tickets@…
     Type:  update          |     Status:  new
 Priority:  Normal          |  Milestone:
Component:  ports           |    Version:  2.3.1
 Keywords:                  |       Port:  rust
----------------------------+--------------------------------
 Rust 0.12 was released on October 9 (https://mail.mozilla.org/pipermail
 /rust-dev/2014-October/011267.html), the current Rust port is 0.12pre from
 September 3, missing about a thousand commits and 20-ish breaking changes.

-- 
Ticket URL: <https://trac.macports.org/ticket/45412>
MacPorts <http://www.macports.org/>
Ports system for OS X