Fix a problem with the runtests target in the C# grade.

Mmake.workspace:
	Don't pass the static archives for the Mercury libraries via --link-object
	(MLOBJS) when building compiler executables and test cases in the C# grade.
	The origin of this setting was (probably) the old il grade; it doesn't
	make sense for the csharp grade however and prevents the test suite from
	working properly in that grade.
More work on running the test suite in non-C grades.

Mmake.workspace:
	Do not set MLOBJS in the java and erlang grades.

tests/warnings/singleton_text.exp[234]:
tests/warnings/warn_succ_ind.exp[234]:
	Update these expected outputs to conform to changes to both the file
	generating the warning and also to the way the Mercury compiler prints
	them.