Add some support to better highlight Rust

It clears some Rust already existing syntax to better highlight the
important language items.

It then relinks some syntax to use the color scheme in a more efficient
way, and it adds some support for types and functions.

Those are the first for the Rust programming language.

colors/odyssey.vim

@@ -302,5 +302,11 @@ call s:h(      'rubyInstanceVariable', 'background',  'warning', 'italic')
 call s:l('rubyInterpolationDelimiter',   'Function')
 call s:l(       'rubyStringDelimiter',   'Constant')
 
+" }}}
+" Rust Highlights {{{
+call s:l(       'rustLifetime', 'Constant')
+call s:l(   'rustQuestionMark', 'Operator')
+call s:l('rustOdysseyFunction', 'Function')
+call s:l(    'rustOdysseyType', 'Type')
 " }}}
 " vim: foldmethod=marker