Fix rust-lang#2973 in Windows CRLF env.

Author: wada314

src/comment.rs

@@ -1304,7 +1304,13 @@ impl<'a> Iterator for LineClasses<'a> {
             None => FullCodeCharKind::Normal,
         };
 
-        while let Some((kind, c)) = self.base.next() {
+        while let Some((kind, mut c)) = self.base.next() {
+            // If \r\n newline appears, consume one more character.
+            // Then do the same process with the single \n case.
+            if c == '\r' && self.base.peek().map_or(false, |(_, c2)| *c2 == '\n') {
+                self.base.next();
+                c = '\n';
+            }
             if c == '\n' {
                 self.kind = match (start_class, kind) {
                     (FullCodeCharKind::Normal, FullCodeCharKind::InString) => {