vim: Support the new \u{1234} unicode escapes

src/etc/vim/syntax/rust.vim

@@ -151,6 +151,7 @@ syn match     rustMacro       '#\w\(\w\)*' contains=rustAssert,rustPanic
 syn match     rustEscapeError   display contained /\\./
 syn match     rustEscape        display contained /\\\([nrt0\\'"]\|x\x\{2}\)/
 syn match     rustEscapeUnicode display contained /\\\(u\x\{4}\|U\x\{8}\)/
+syn match     rustEscapeUnicode display contained /\\u{\x\{1,6}}/
 syn match     rustStringContinuation display contained /\\\n\s*/
 syn region    rustString      start=+b"+ skip=+\\\\\|\\"+ end=+"+ contains=rustEscape,rustEscapeError,rustStringContinuation
 syn region    rustString      start=+"+ skip=+\\\\\|\\"+ end=+"+ contains=rustEscape,rustEscapeUnicode,rustEscapeError,rustStringContinuation,@Spell
@@ -187,7 +188,7 @@ syn match   rustCharacterInvalid   display contained /b\?'\zs[\n\r\t']\ze'/
 " The groups negated here add up to 0-255 but nothing else (they do not seem to go beyond ASCII).
 syn match   rustCharacterInvalidUnicode   display contained /b'\zs[^[:cntrl:][:graph:][:alnum:][:space:]]\ze'/
 syn match   rustCharacter   /b'\([^\\]\|\\\(.\|x\x\{2}\)\)'/ contains=rustEscape,rustEscapeError,rustCharacterInvalid,rustCharacterInvalidUnicode
-syn match   rustCharacter   /'\([^\\]\|\\\(.\|x\x\{2}\|u\x\{4}\|U\x\{8}\)\)'/ contains=rustEscape,rustEscapeUnicode,rustEscapeError,rustCharacterInvalid
+syn match   rustCharacter   /'\([^\\]\|\\\(.\|x\x\{2}\|u\x\{4}\|U\x\{8}\|u{\x\{1,6}}\)\)'/ contains=rustEscape,rustEscapeUnicode,rustEscapeError,rustCharacterInvalid
 
 syn region rustCommentLine                                        start="//"                      end="$"   contains=rustTodo,@Spell
 syn region rustCommentLineDoc                                     start="//\%(//\@!\|!\)"         end="$"   contains=rustTodo,@Spell