Merge pull request rust-lang#30 from Stebalien/master

Once isn't a keyword.

Author: chris-morgan

syntax/rust.vim

@@ -24,7 +24,7 @@ syn keyword   rustKeyword     continue
 syn keyword   rustKeyword     extern nextgroup=rustExternCrate,rustObsoleteExternMod skipwhite skipempty
 syn keyword   rustKeyword     fn nextgroup=rustFuncName skipwhite skipempty
 syn keyword   rustKeyword     for in if impl let
-syn keyword   rustKeyword     loop once pub
+syn keyword   rustKeyword     loop pub
 syn keyword   rustKeyword     return super
 syn keyword   rustKeyword     unsafe where while
 syn keyword   rustKeyword     use nextgroup=rustModPath skipwhite skipempty