rollup merge of rust-lang#19784: csouth3/vim-syntax-iter

Vim still incorrectly highlights just `ExactSize` as a valid trait name, but the trait has been renamed to `ExactSizeIterator`.

Author: brson

src/etc/vim/syntax/rust.vim

@@ -90,7 +90,7 @@ syn keyword rustTrait Clone
 syn keyword rustTrait PartialEq PartialOrd Eq Ord
 syn keyword rustEnum Ordering Equiv
 syn keyword rustEnumVariant Less Equal Greater
-syn keyword rustTrait FromIterator Extend ExactSize
+syn keyword rustTrait FromIterator Extend ExactSizeIterator
 syn keyword rustTrait Iterator DoubleEndedIterator
 syn keyword rustTrait RandomAccessIterator CloneableIterator
 syn keyword rustTrait OrdIterator MutableDoubleEndedIterator