libkernelland_emu: Remove deleted scheduler.cpp from build.

The file was removed in hrev47484, but the Jamfile wasn't updated.
libkernelland_emu: Sync _rw_lock_{read|write}_unlock API.

The threadsLocked parameter was removed from the kernel API.
libkernelland_emu: Fix missing using namespace std for GCC4.
libkernelland_emu: Fix wrong return in ModuleList::AddModule().
btreeTest: Revive test for BPlusTree implementation.

* Update pseudo cache with minimal set of block cache API.
* Update Inode, Journal and Volume stubs to current API.
* Add stubs for remaining VFS functions.
* Extend tests to also call BPlusTree::Validate() and bail on errors.
* Change duplicate tests to fill in the same value. While this isn't
  strictly allowed, the tree validation can't work unless the values
  match up.
* Lots of coding style cleanup, but much more should still be done...

The tests run through without errors.