[BUG #7708] add inverse(), minor comments
[BUG #7708] renamed ident_is_ignored to name_is_jsignored, replaced filter methods
(this commit is broken on its own! (bc. of the rename))

- replaced collection-base filters with single-element predicates
  (filters weren't used anyway)
  - globals_fiter_by_libclasses -> test_ident_is_libsymbol
  - globals_filter_by_hints -> test_ident_is_jsignored
  - () -> test_ident_is_builtin
-minor comments
[BUG #7708] using the new filter predicates from the global_symbols module

- only needing some local helper functions for fitting
- arrangning them in a util/pipeline, for clearer data flow
- commenting out other unused code