ramfs: Fix miscellaneous warnings.

ramfs: Adapt to current kernel FS APIs and fully fix the build.

ramfs: Add MIT license header to all files lacking copyright info.

OK'ed by Ingo via email.

ramfs: Lots of fixes to the build.

* Store pointers in an addr_t instead of int32, for 64-bit's sake
* Use DebugSupport.h instead of userlandfs Debug.h and remove extra parentheses
* Create a header-only String class based on the userlandfs String and use it
* RecursiveLock instead of Locker.
* Jamfile cleanups and other misc. changes.

It isn't yet adapted to the new VFS API, so the build is still somewhat
broken.