This implements Mantis feature request #497.
compiler/parse_goal.m:
compiler/parse_dcg_goal.m:
When we find that a disable_warnings scope contains an unrecognized
warning name, generate a warning for it, and return this warning
*alongside*, not *instead of*, the disable_warnings scope goal.
This requires passing around not a maybe1(goal), as we have been doing
till now, but a maybe2(goal, list(warning_spec)), so this change
affects both (1) most of these two modules, and (2) most of the
modules below.
compiler/error_util.m:
Provide warning_spec as a synonym for error_spec, to be used in
situations like this where the "error_spec" is intended contain
something with severity_warning.
compiler/maybe_error.m:
Provide some new utility predicates now needed in parse_goal.m
and elsewhere.
compiler/prog_item.m:
Provide room in the representation of clauses for the warnings
generated by parsing the clause body goal.
compiler/add_class.m:
compiler/add_clause.m:
compiler/add_mutable_aux_preds.m:
compiler/add_pragma_tabling.m:
compiler/du_type_layout.m:
compiler/get_dependencies.m:
compiler/make_hlds_passes.m:
compiler/parse_item.m:
compiler/parse_tree_out_clause.m:
compiler/prog_item_stats.m:
compiler/superhomogeneous.m:
Conform to the changes above.
tests/valid/unknown_warning.m:
Add this test case that checks whether a source file with an unknown
warning name in a disable_warnings scope can have code generated for it.
tests/warnings/unknown_warning.{m,exp}:
Add the same source file to this directory as well, to check whether
we get the right set of warnings.
tests/valid/Mmakefile:
tests/valid/Mercury.options:
tests/warnings/Mmakefile:
Enable the two new test cases.
