geometry.index: pack_create - non-VC-compiler compilation errors fixed, small optimization added.

svn path=/trunk/boost/geometry/; revision=84722
geometry.index: packer - nodes counts container removed. counts are calculated when needed, subtree_counts pair replaced by struct with descriptive members and trivial copy.

svn path=/trunk/boost/geometry/; revision=84724
[geometry] Iterator difference is not always std::size_t

svn path=/trunk/boost/geometry/; revision=84726
[geometry] Add message missing in BOOST_ASSERT_MSG

svn path=/trunk/boost/geometry/; revision=84727
geometry.index: packer replaced by pack, various tweaks added.

svn path=/trunk/boost/geometry/; revision=84730