[folding] Allow folding block comment that starts in the middle of the line

An additional request on top of now-closed feature-request [11524](https://github.com/Microsoft/vscode/issues/11524). I sometimes like to write my block comments in this form: ``` let someflag : boolean = false;/* this flag does blah blah blah blah blah blah*/ let somethingelse : string; ``` So that folding that comment completely removes it from view outside of that trailing start marker. However, the implementation to feature-request 11524 does not detect this type of block comment and only seems to pick up on block comments started on their own new line. I am not sure how popular that style of commenting is, but it would help me a lot of it could be picked up by that feature. Thanks.