[ new ] Agda.Utils.Bag for sets with duplicates.
[ new ] Null instance for Bag.
[ refactor ] Utils.List.uniqBy to uniqOn with Map implementation.
[ opt ] Small optimization in Utils.List.sorted.

inits is not needed here as zipWith disregards the tail of the longer list.
[ new ] Agda.Utils.List.duplicates.

Faster than nub (xs \\ nub xs).
[ debug ] Prettier printing of patterns in Coverage.
[ refactor ] Use duplicates, unlessNull in ConcreteToAbstract.
[ Errors ] Changed error message for non-linear patterns.

No longer talkes about `left hand side' as this would be confusing for
pattern synonyms (where the pattern is on the right hand side).
[ Issue 1295 ] Fixed by checking linearity of pattern synonym.
[ Issue 1295 ] Test case.
Merge branch 'maint-2.4.2'
[ Issue 1299 ] Fixed module macros in telescopes.

1. If module macros are present in module telescope, we need protective
anonymous module wrapped around the module (as for open statements).
2. Module macros in lets need to be private.
[ Issue 1299 ] Test case.
Merge branch 'maint-2.4.2'