JSC Obj-C API should have real documentation
https://bugs.webkit.org/show_bug.cgi?id=124805

Reviewed by Geoffrey Garen.

Massaging the header comments into proper headerdocs.

* API/JSContext.h:
* API/JSExport.h:
* API/JSManagedValue.h:
* API/JSValue.h:
* API/JSVirtualMachine.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@159723 268f45cc-cd09-0410-ab3c-d52691b4dbfc