etc: Add box as a keyword to editor configs

This keyword is about to be used much more often than it was a few weeks ago,
it's time to tell editors about the new keyword.

src/doc/rust.md

@@ -204,7 +204,7 @@ The keywords are the following strings:
 
 ~~~~ {.notrust .keyword}
 as
-break
+box break
 crate
 else enum extern
 false fn for

src/etc/gedit/share/gtksourceview-3.0/language-specs/rust.lang

@@ -38,6 +38,7 @@
 		<keyword>as</keyword>
 		<keyword>assert</keyword>
 		<keyword>break</keyword>
+		<keyword>box</keyword>
 		<keyword>const</keyword>
 		<keyword>continue</keyword>
 		<keyword>crate</keyword>

src/etc/kate/rust.xml

@@ -18,6 +18,7 @@
 	<list name="keywords">
 		<item> as </item>
 		<item> break </item>
+		<item> box </item>
 		<item> continue </item>
 		<item> crate </item>
 		<item> do </item>

src/etc/vim/syntax/rust.vim

@@ -18,7 +18,7 @@ syn keyword   rustOperator    as
 
 syn match     rustAssert      "\<assert\(\w\)*!" contained
 syn match     rustFail        "\<fail\(\w\)*!" contained
-syn keyword   rustKeyword     break continue
+syn keyword   rustKeyword     break box continue
 syn keyword   rustKeyword     extern nextgroup=rustExternCrate,rustObsoleteExternMod skipwhite
 syn keyword   rustKeyword     for in if impl let
 syn keyword   rustKeyword     loop once priv pub