compat: Remove handling of Lua 5.1 location of 'unpack' function

Merge 0.12->trunk

luacheck: Set expected globals to Lua 5.4 + compat Requires luacheck 0.25.0

core.s2smanager: Don't remove unrelated session on close of bidi session Normally with bidi, any outgoing connection should be the same as the incoming, hence when closing a bidi connection it should be removed as a route to the remote server. However it is not guaranteed, a remote bidi-capable server might have decided to open a new connection for some reason. This can lead to a situation where there are two bidi connections, and the s2sout route is a locally initiated s2sout connection. In this case, such a s2sout connection should be kept. Noticed in a rare case where bidi has just been enabled on a running server, and something establishes new connections immediately when a connection is closed.

Merge 0.12->trunk

luacheck: Shut up (backports 3caff1f93520, ignores module deleted in trunk)

Merge 0.12->trunk

Backport 875f73ead4e8 8e4033213c62 to deal with luacheck 0.26

Merge 0.12->trunk

util.datamapper: Improve handling of schemas with non-obvious "type" The JSON Schema specification says that schemas are objects or booleans, and that the 'type' property is optional and can be an array. This module previously allowed bare type names as schemas and did not really handle booleans. It now handles missing 'type' properties and boolean 'true' as a schema. Objects and arrays are guessed based on the presence of 'properties' or 'items' field.