c++/modules: Fix missed unwrapping of STAT_HACK in ADL [PR121893]

c++/modules: Fix missed unwrapping of STAT_HACK in ADL [PR121893]

My r16-3559-gc2e567a6edb563 reworked ADL for modules, including a change
to allow seeing module-linkage declarations if they only exist on the
instantiation path.  This caused a crash however as I neglected to
unwrap the stat hack wrapper when we were happy to see all declarations,
allowing search_adl to add non-functions to the overload set.

	PR c++/121893

gcc/cp/ChangeLog:

	* name-lookup.cc (name_lookup::adl_namespace_fns): Unwrap the
	STAT_HACK also when on_inst_path.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/adl-10_a.C: New test.
	* g++.dg/modules/adl-10_b.C: New test.

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