Use BStringList in package kit

Replace all instances of BObjectList<BString> by BStringList.
Removed left-over code
Pull class BPackageInfoSet out of BRepositoryCache
find_directory(): Fix package links path
Add class BPackageInfoContentHandler

A BPackageContentHandler subclass that initializes a BPackageInfo from
the read package attributes. Pulled out of RepositoryWriterImpl's
PackageContentHandler.
Add BPackageRoster::GetActivePackages()

The implementation is temporary. Currently it reads through the packages
in the respective packages directory and checks against the package
links. Once package activation is tracked explicitly we'll use the
activation file/directory.
Fix build due to <directories.h> move

Apparently I should have done a complete rebuild after moving
directories.h from headers/private/libroot to .../system, since a lot of
stuff didn't build anymore.
configure: Update required gcc 2 version
Repackage BeZillaBrowser as hpkg
Fix typo
Fix package removal with skipped directories

Volume::_RemovePackageContentRootNode(): Check whether a directory
corresponding to the package directory does actually exist. This might
not be the case when the package directory has been skipped due to
clashing with a shine-through directory. Would crash in this case.
Fix node handling on package addition/removal

* UnpackingLeafNode: Add a fFinalPackageNode attribute. It is set when
  the node is about to be removed and will point to the node's previous
  head package node and be used in its stead. From the perspective of
  the FS hooks this leaves the node in an unchanged state.
* Unpacking[Leaf,Directory]Node:
  - Add WillBeFirstPackageNode(), returning whether the given package
    node would become the head package node when added.
  - Add PrepareForRemoval() which removes all package nodes. In case of
    UnpackingLeafNode it also sets fFinalPackageNode.
  - Add CloneTransferPackageNodes(). It is only implemented for
    UnpackingLeafNode. It clones the node, transfers all package nodes
    to the clone and sets fFinalPackageNode on this node.
* Volume::_{Add,Remove}PackageNode(): Solved the following TODO: When a
  package is added or removed and a file present in both the
  added/removed package and another package with the version in the
  former having precedence, we have to remove the node (leaving it
  unchanged) and replace it by a new node. This prevents clients having
  the node opened or mapped from suddenly seeing different data. It also
  fixes unbalanced calls to PackageNode::VFSInit()/VFSUninit() which
  would result in file descriptors to package files being leaked.
Fix removing dependencies on package removal

The dependencies must also be dissociated from the resolvables they have
been resolved to.
Node: Keep track of VFS init status

* Node::VFSInit() and VFSUninit() set/clear the new node flag
  NODE_FLAG_KNOWN_TO_VFS. They need to be called by overriding methods,
  now.
* Add Node::IsKnownToVFS() which returns the VFS init status.
Volume::_RemoveNodeAndVNode(): Squash TODO

Only get/remove/put the vnode when the node is actually known to the
VFS. This does not only save unnecessary work, it also solves a
(temporary) deadlock -- at least partially. If another thread caused a
call to our get_vnode() hook just before, it would block on the volume
lock we're holding when adding/removing packages. The vnode would be
marked busy until the other thread's request was fulfilled and our call
to get_vnode() would block until timing out. Now we're calling
get_vnode() only, if we already know that the VFS already has a valid
vnode.

There still remains a race condition. If the VFS discards the vnode
right before we call get_vnode(), we essentially have the same situation
as before (i.e. us calling get_vnode() although the vnode is no longer
known to the VFS) with the same potential problem. For a real solution
we need a get_vnode() variant which can be told not to block.
Merge branch 'master' into pm-flat

Conflicts:
	build/jam/HaikuImage
	build/jam/OptionalBuildFeatures
	build/jam/OptionalPackages
	build/jam/UserBuildConfig.sample
	data/bin/installoptionalpackage
	src/apps/deskbar/DeskbarMenu.cpp
	src/servers/debug/DebugServer.cpp
	src/system/kernel/fs/vfs.cpp
PackageLinkDirectory::_Update(): Don't unlock after delete

When using an AutoLocker on an object, the lock must be released
explicitly before releasing the last certain reference to that object.
haiku package info: declare a few provided commands

sh, awk, wget, etc. are currently provided by haiku.hpkg. Declare
them accordingly, since they are already referenced by some
HaikuPorts packates. For the generic ones ("sh", "awk") I've used
version 0.0.0 for the time being; we may need to reconsider that.
Repackaged xz-utils package

It is now declared with architecture x86_gcc2, though it probably
has been built with gcc4. That issue has to be solved for real
eventually, since the package resolver won't allow mixing of gcc2
and gcc4 packages.
haiku package info: Add more provided resolvable

Also add a compat version to a few.