(vfs_s_close): vfs-specific data of file handler
vfs_file_handler_t::data is freed in vfs_s_subclass::fh_close method and
then can be used in vfs_s_subclass::file_store_one. Bug is related to
ftp and fish VFSes.
Added new vfs_s_subclass::fh_free_data method to free vfs-specific data
of file handler vfs_file_handler_t::data. Use it in ftp and vfs VFSes.
Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
664b3efcda