Tweak visibility of abstract_die methods in iterator_base.
Support string-to-number mappings in spec.
find_attr tweaks, and deal with DW_TAG_unspecified_type.
frame: deal with DW_CFA_GNU_args_size opcode.
Makefile tweaks.
Some Makefile fixes.
Actually do meaningful string comparisons during string-to-number spec lookups.
Tweaks to in-memory DIEs: can now be contained within ordinary root_dies.