Reintroduce elf.Segments(): speeds up symbol checking from 21.7 to 17.0 s

Though it’s still much slower than 5.9 s, before “pyelftools” was used
Alias --dry-run of --dryrun
Symbol resolution too damn slow
Verbose dependency analysis option
Handle PLT relocations
Merge branch 'elf'
Seems the GNU and “none” ABIs are compatible both ways