cxxll::dwarf::error: Introducer setter function for data member
cxxll/dwarf/error.hpp: Fix header file preamble
cxxll::dwarf::error::code(): New member function
cxxll::elf_image::dwarf_cu_range: Report libdw error codes
SQL schema: Add column symboldb.dwarf_error.code
database::add_dwarf(): Record libdw error codes in database
Add test coverage for libdw error codes