Allow more kinds of @suppress on non-function nodes.

Most of the lint warnings from Closure Library are "@suppress is not allowed here", and many of the use cases seem reasonable to me. Eg.:

``` js
/** @suppress {unusedLocalVariables} */
var dummy = 3;
```

We also need to document where @suppress is actually allowed, pending TODO by @MatrixFrog in https://github.com/google/closure-compiler/blob/master/src/com/google/javascript/jscomp/lint/CheckJSDocStyle.java#L45-L48.