Remove dwarf2_per_cu_data::v

Remove dwarf2_per_cu_data::v

Now that the psymtab reader has been removed, the
dwarf2_per_cu_data::v union is no longer needed.  Instead, we can
simply move the members from dwarf2_per_cu_quick_data into
dwarf2_per_cu_data and remove the "quick" object entirely.