(refs #9) Redefine hash-table as (or cl:hash-table abstract-hash-table).
(refs #9) Redefine sequence as (or cl:sequence abstract-sequence).
(refs #9) Add abstract-fill.
Move every, some, notevery and notany from core to core.sequence.
Redefine second, third ... tenth as generic functions.
Redefine every, some, notevery and notany to be able to work with abstract-sequences.
Change the behavior of push, pushnew and pop for vectors.

Though vector-push pushes to the end of a sequence, it makes us
confused.
Make push, pushnew and pop allow to take abstract-sequences.