When building contrib/hpack there is a warning about an unused static
function. Actually it makes no sense to make it static, instead it must
be regularly exported. Similarly there is hpack_dht_get_tail() which is
inlined in the C file and which would make more sense with all other ones
in the H file.
The various hpack files are self-contained, but hpack-tbl was one of
those showing difficulties when pools were added because that began
to add quite some dependencies. Now when built in standalone mode,
it still uses the bare minimum pool definitions and doesn't require
to know the prototypes anymore when only the structures are needed.
Thus the files were moved verbatim except for hpack-tbl which was
split between types and prototypes.
