PR symtab/16426

	* dwarf2read.c (dwarf2_get_dwz_file): Call gdb_bfd_record_inclusion.
	(try_open_dwop_file): Ditto.
	* gdb_bfd.c: #include "vec.h".
	(bfdp): New typedef.
	(struct gdb_bfd_data): New member included_bfds.
	(gdb_bfd_unref): Unref all included bfds.
	(gdb_bfd_record_inclusion): New function.
	* gdb_bfd.h (gdb_bfd_record_inclusion): Declare.
Use bitpos and type to lookup a gdb.Field object when its name is 'None'.

	PR python/15464
	PR python/16113
	* valops.c (value_struct_elt_bitpos): New function
	* py-type.c (convert_field): Set 'name' attribute of a gdb.Field
	object to 'None' if the field name is an empty string ("").
	* python/py-value.c (valpy_getitem): Use 'bitpos' and 'type'
	attribute to look for a field when 'name' is 'None'.
	(get_field_type): New function

	testsuite/
	* gdb.python/py-type.c: Enhance test case.
	* gdb.python/py-value-cc.cc: Likewise
	* gdb.python/py-type.exp: Add new tests.
	* gdb.python/py-value-cc.exp: Likewise