properly calculate if we need to expand the header block in spdy_header_block_add().
properly calculate if we need to expand the header block in spdy_header_block_add().

zhcy/kore,hhua/kore,jorisvink/kore,bonifaido/kore,fourdollars/kore,sinemetu1/kore,jorisvink/kore,korusdipl/kore,bonifaido/kore,bonifaido/kore,hhua/kore,hhua/kore