Cleanup follow-up: Delete code for shared integers

[zuiderkwast]

With this change (#1186), I'm fairly sure we never used shared objects anywhere in the codebase anymore. We might want to cleanup that code (can be a followup) to make sure we don't silently introduce bugs there and then forget about them if we use them again.

Originally posted by @madolson in #1186 (comment)

Update: We do use shared objects (string objects like shared.ok) but not shared integers, apart from a zero reply of some command.