libdw: Update acceptable forms and attributes for dwarf_getlocation.

libdw: Update acceptable forms and attributes for dwarf_getlocation.

dwarf_getlocation has to know which attributes can contain a DWARF
expression or location list because the form alone might be ambiguous.

Since DWARF4 there is DW_FORM_exprloc so always accept that. But for older
DWARF or location lists we cannot just check for DW_FORM_sec_offset since
that could be a reference to diffent kinds of sections (based on attribute).

Update the attribute list based on the latest DWARF5 encodings table.
Note that DW_AT_call_origin wasn't added because that seems to be a
typo in the DWARF5 spec. http://dwarfstd.org/ShowIssue.php?issue=171103.1

Signed-off-by: Mark Wielaard <mark@klomp.org>