2. Section headers and symbol tables - done

selfish-elf::section reads section headers, the name table, section contents, and .symtab with its strings. Cross-checked against readelf on a real linked object: 14,667 entries and 74 undefined, exactly.

defines(name) is the thing a builder actually needs - whether the object defines a symbol, which is what decides whether an initialiser tag belongs in the dynamic table. (D023)