auto merge of #9936 : madjar/rust/master, r=alexcrichton

This should close #9468.

I removed the test stating that nested comments should not be implemented.

I had a little chicken-and-egg problem because a comment of the std contains "/*", and adding support for nested comment creates a backward incompatibility in that case, so I had to use a dirty hack to get stage1 and stage2 to compile. This part should be revert when this commit lands in a snapshot.

This is my first non-typo contribution, so I'm open to any comment.

src/test/run-pass/nested-block-comment.rs

@@ -8,19 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern:
-
-/* This is a test to ensure that we do _not_ support nested/balanced comments. I know you might be
-   thinking "but nested comments are cool", and that would be a valid point, but they are also a
-   thing that would make our lexical syntax non-regular, and we do not want that to be true.
-
-   omitting-things at a higher level (tokens) should be done via token-trees / macros,
-   not comments.
+/* This test checks that nested comments are supported
 
    /*
-     fail here
+     This should not fail
    */
 */
 
-fn main() {
+pub fn main() {
 }