This continues the cleanup of the 'htools' name, by replacing 'htools'
with 'hs' in configure and makefile rules.

There is still 'WANT_HTOOLS' left as it is correct, but some of the
conditionals in Makefile.am will need some cleanup (in a different
patch).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>