- Always load files when cleaning up jumplist.
- For Shada: avoids writing duplicate entries, which happens when you read
from a shada file with duplicate entries (merging the jumplist while
writing sometimes produces duplicate entries, bug?) and then write right
away (i.e.: without any `:jumps`, `getjumplist()`, or any jump movement,
that is: nothing that calls `cleanup_jumplist` with `loadfiles == true`).
- For Context: avoids non-idempotent behavior for the same reason (i.e.:
first call to `shada_encode_jumps` does not remove duplicate entries).
- Do not set pcmark when dumping jumplist for Context.
- Retrieving current Context shouldn't add an entry to the jumplist
(which will be removed by a subsequent `cleanup_jumplist` anyway, i.e.:
tail entry matching current position), just act like `getjumplist` for
instance.
