vim: Add pure to the list of keywords

Author: pcwalton

src/etc/vim/syntax/rust.vim

@@ -18,8 +18,8 @@ syn keyword   rustKeyword     alt as assert auth be bind break chan check
 syn keyword   rustKeyword     claim cont const do each else export fail fn for
 syn keyword   rustKeyword     if import in inline iter lambda let log log_err
 syn keyword   rustKeyword     macro meta mod mutable native note obj port
-syn keyword   rustKeyword     prove put resource ret self spawn syntax tag
-syn keyword   rustKeyword     type unsafe use while with
+syn keyword   rustKeyword     prove pure put resource ret self spawn syntax
+syn keyword   rustKeyword     tag type unsafe use while with
 
 syn keyword   rustType        any int uint float char bool u8 u16 u32 u64 f32
 syn keyword   rustType        f64 i8 i16 i32 i64 str task