Import aliases(imports are confusing things about some libraries)

Looks like yet one reincarnation of ‘@exported imports’.
(proposal with implementation: https://docs.google.com/document/d/1dlT6NgB9610jqLscCJW2LRB7TapDh3q4d2S3YA_q5zs/edit
Last discussion here: Pre-SIP: export, dual* of import
)
// about further progress/development, I think it is possible to revive this proposal (i.e. submit this PRE-SIP) if we will know, that exists enough interest for such feature within community and compiler maintainers.