PackageLinkSymlink: Init fLinkPath in constructor
NodeListener::NodeChanged(): Provide old value

* Add interface OldNodeAttributes an instance of which is passed to
  NodeListener::NodeChanged() to provide the old attribute values
  (currently only modification time and file size).
* Also extend PackageLinksListener::PackageLinkNodeChanged() with a
  OldNodeAttributes parameter.
* Add OldNodeAttributes implementations for PackageLinkSymlink (inner
  class OldAttributes) and UnpackingNode (OldUnpackageNodeAttributes).
Refactor NameIndexIterator into template class

Create template class GenericIndexIterator from NameIndexIterator.
Small cleanup
TwoKeyAVLTree: Add FindFirstClosest()
GenericIndexIterator: Fix NameIndex dependency

Next() was still copying the name. Add a GetNodeValue() method to the
policy that fetches the value instead.
GenericIndexIterator::SetTo(): Find fuzzily

Use TwoKeyAVLTree::FindFirstClosest() instead of FindFirst(), so, if the
value isn't in the index, we find the closest greater value. That's the
semantics Index::InternalFind() is expected to have.
Add comment
GenericIndexIterator: Add node change helpers

Add NodeChangeBegin()/NodeChangeEnd() methods that can be used by the
index when the respective node attribute has changed. They make sure
that the iterator doesn't move with the node, should it be inserted into
the index at a different position.
Add size index support

* Add class SizeIndex.
* Create and add an instance of it in Volume mount.
QueryParser: The last_modified index is time_t

* Changed value type from B_INT64_TYPE to B_INT32_TYPE.
* Changed QueryPolicy::NodeGetLastModifiedTime() return value from
  bigtime_t to time_t.
Removed left-over commented code
Add last modified index support

* Add class LastModifiedIndex.
* Create and add an instance of it in Volume::Mount().
Build fix
AVLTreeMap fixes

* AVLTreeMap::_GetKey(): Change return type from const Key& to Key, so
  the strategy can do that as well and doesn't have have a Key object in
  the node.
* Fix the Auto strategy: It was using the undefined _GetKey() instead
  of GetKey().
Move helper function out of QueryParser.h

They live in the new QueryParserUtils.{h,cpp} now.
Remove TwoKeyAVLTree from kernel utils again

It's not ready for shared use yet.
Move B_MIME_STRING_TYPE to <TypeConstants.h>
compareKeys(): Also handle B_MIME_STRING_TYPE
Remove unused PackageNodeAttribute::fParent