Prefer BOOST_CPPFLAGS and BOOST_CXXFLAGS to corresponding ICU flags, which helps with include paths.
Be more specific about lib paths to help out broken old Ubuntu.
Add lg_search_resolve, and have it and lg_search return the current left-most offset in the stream still being considered for the start of a potential hit, or MAXUINT64 if there aren't any. lg_search_resolve() enables parallel searching [for the right pattern sets].