autotools: detect proper boost sleep in configure

Additionally, link in boost_crypto if necessary.
autotools: change ARG_ENABLE to ARG_WITH for dependencies
autotools: fix broken output when qt is disabled
autotools: don't check for qrencode if qt is disabled
autotools: check for bdb headers and cosmetics
autotools: remove frandom-seed. Let gitian set it.
autotools: move flags to rhs of configure
autotools: fixup comment