ck_bag: Drop support for this data structure.

Could not find suitable use-case and generally doesn't
appear interesting to academics in the existing
form. Maybe it will make a come-back in the future with
fewer memory and latency compromises.
doc: Fix ck_hs_next reference.

Patch submitted by Devon H. O'Dell.
doc: ck_cohort: Fix example & function signatures.
doc: CK_COHORT_PROTOTYPE: Remove descriptions for unexisting parameters.
doc: ck_sequence: Fix header & function names.
doc: ck_elide: Fix typos.
doc: ck_epoch_call: Insert empty string between type definitions.
doc: ck_hs_remove: Rectify an argument name.