c++: Seed namespaces for bindings [PR106363]

c++: Seed namespaces for bindings [PR106363]

Currently the first depset for an EK_BINDING is not seeded. This breaks
the attached testcase as then the namespace is not considered referenced
yet during streaming, but we've already finished importing.

There doesn't seem to be any particular reason I could find for skipping
the first depset for bindings, and removing the condition doesn't appear
to cause any test failures, so this patch removes that check.

	PR c++/106363

gcc/cp/ChangeLog:

	* module.cc (module_state::write_cluster): Don't skip first
	depset for bindings.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/pr106363_a.C: New test.
	* g++.dg/modules/pr106363_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>