[ .cabal ] Added lower bound for the parallel library

(Travis uses parallel 3.2.0.4 with all the versions of GHC)
Merge branch 'maint-2.4.2'
[ refactor ] Removed useless expandEllipsis from ConcreteToAbstract
(Ellipsis are already expanded in Syntax.Concrete.Definitions)
Merge branch 'maint-2.4.2'
[ Issue 1379 ] Fixed the range of with clauses starting with an ellipsis.
[ refactor ] Removed unused last argument from SplitError.CantSplit.
[ refactor ] Use whenJust and <.>.
[ comment ] Agda.Utils.NubList is UNUSED.
[ new ] Agda.Utils.Singleton replaces Agda.Utils.Pointed.

Overloaded method `singleton` constructs singleton collections of
various types.  Analogous to Agda.Utils.Null.
[ Issue 1084 ] Fixed by removing function names that do not appear in offending calls.

Termination errors should now only be reported for functions that
actually contribute to potential cycles.
[ Issue 1084 ] Updated error messages in test/fail.
[ Issue 1084 ] Test case.

Already covered by test cases for 921 and 1375, but it is clearer to
have a native test case.
[ refactor ] Null, Singleton instances for Favorites, CMSet, CallGraph.
[ comment ] Attempt to add callSource to CallPath (abandoned).
Merge branch 'maint-2.4.2'
[ Utils.Singleton ] forgot to add file.
Merge branch 'maint-2.4.2'
Merge remote-tracking branch 'upstream/master'