Extend workaround in 142660c to accept all abbrevations of :quit
Extend redundant-import trigger to support qualified imports

The redundant-import-removal-suggest feature added in 741ab38 has two
deficiencies:

 - doesn't trigger in case of multi-line warnings (happens with GHC 7.6), and
 - doesn't trigger in case of qualified imports.

This commit tries to address these two issues by improving the regexp
providing the trigger.