Fixes #requires_redmine comments (#12299).
Makes Plugin#requires_redmine accept a range of versions (#12299).
Makes Plugin#requires_redmine accept only major and minor version (#12299).
Rewrites requires_redmine tests.
Merged r10745 from trunk (#12231).
Merged r10806 from trunk (#12195).
Backported r10792 and r10793 from trunk (#12310).
Merged r10810 from trunk (#12359).
Merged r10790 from trunk (#12294).
Merged r10801 from trunk (#12349).
