v0.8.0

Changed

• Patterns are parsed once per search: seagrep_core::parse_pattern produces
  the Hir consumed by seagrep_query::plan_hir, can_search_as_document,
  and bounded_match_len (the latter two now take &Hir instead of &str),
  so the planner and the grep-mode analyses cannot disagree about a pattern.