re PR debug/27017 (Debug information for static local class members are not emitted)

	PR c++/27017
	* dwarf2out.c (prune_unused_types_walk_local_classes): New function.
	(prune_unused_types_walk): Call it for non-perennial local classes.
	Set die_mark to 2 if recursing on children.  If die_mark is 1 on
	entry, just set it to 2 and recurse on children, don't walk attributes
	again.

	* g++.dg/debug/dwarf2/localclass1.C: New test.
	* g++.dg/debug/dwarf2/localclass2.C: New test.

From-SVN: r141829