Generalize the SpinLock and move it to AK.

Add a separate lock to protect the VFS. I think this might be a good idea.
I'm not sure it's a good approach though. I'll fiddle with it as I go along.

It's really fun to figure out all these things on my own.

VirtualFileSystem/test.cpp

@@ -21,6 +21,8 @@ int main(int c, char** v)
     if (c >= 2)
         filename = v[1];
 
+    VirtualFileSystem::initializeGlobals();
+
     VirtualFileSystem vfs;
 
     auto zero = make<ZeroDevice>();