Link import statements

[felix-hilden]

Discussed in #29: we could also link import statements. It can only make things better. Let's do:

import mod.sub  # mod.sub
import mod.sub as s  # mod.sub, not "as s"
from mod.sub import foo as f  # foo, not "as f"
from mod.sub import *  # nothing linked

[Zac-HD]

from mod.sub import foo as f  # foo, not "as f"
from mod.sub import *  # nothing linked

Might as well link mod.sub in these cases too; it's not like we can run out of hyperlinks!