[ refactor ] Removed useless expandEllipsis from ConcreteToAbstract
(Ellipsis are already expanded in Syntax.Concrete.Definitions)
[ 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).
[ Utils.Singleton ] forgot to add file.
[ comments ] and whitespace only.
[ clarify ] some obfuscated code plus simple rewrites.
[ compilation ] Forgotten TupleSections pragma.
[ Issue 1379 ] Fixed the range of with clauses starting with an ellipsis.
[ cosmetics ] Broke a too long line.
[ interaction ] Show also open instance metas.

Could not see any effect on the interaction test suite.
[ clean ] Removed some old, commented out code.
[ optim ] Use raiseS in construction of substitution.
[ clarify ] Some rewriting of the code for with display form generation.