libs: use buxfix jpnfs-0.5.8

    * [968bdd3] core: limit number of states owned by client
    * [9f9863a] vfs: use inodeToBytes to generate file handle for chimera

exclude h2 dependency

Target: 2.6
Require-book: no
Require-notes: no
Merge pull request #258 from kofemann/jpnfs-0.5.8-for-2.6

libs: use buxfix jpnfs-0.5.8