PR symtab/18258
gdb/ChangeLog:
	* block.c (block_find_symbol): New function.
	(block_find_non_opaque_type): Ditto.
	(block_find_non_opaque_type_preferred): Ditto.
	* block.h (block_symbol_matcher_ftype): New typedef.
	(block_find_symbol): Declare.
	(block_find_non_opaque_type): Ditto.
	(block_find_non_opaque_type_preferred): Ditto.
	* dwarf2read.c (dw2_lookup_symbol): Call block_find_symbol.
	* psymtab.c (psym_lookup_symbol): Ditto.
	* symtab.c (basic_lookup_transparent_type_1): New function.
	(basic_lookup_transparent_type): Call it.
gdb/testsuite/ChangeLog:
	* gdb.dwarf2/opaque-type-lookup-2.c: New file.
	* gdb.dwarf2/opaque-type-lookup.c: New file.
	* gdb.dwarf2/opaque-type-lookup.exp: New file.