Changes:
* Terminate all namespaces with the correct closing comment.
* Make sure argument names in comments match the corresponding parameter name.
* Remove redundant get() calls on smart pointers.
* Prefer using "override" or "final" instead of "virtual". Remove "virtual" where appropriate.
The underlying mechanism uses darwin's libcache library (if not building on darwin there is a default implementation).
This was originally introduced in SourceKit, but we are moving it to libswiftBasic so it can be utilized by libswiftIDE
for caching code-completion results.
Swift SVN r9610
