…Info struct

…r (SHT_GNU_verdef) section

To get started commit binaries ...

Implement some std traits:
    - IntoIter
    - ExactSizeIterator
    - FusedIterator

Rename iterator structs similar to std.

Add inline attributes.

…d (SHT_GNU_verdef) section + doc example

Use sub-module rather than macro to implement feature guard, as
`cargo fmt` doesn't seem to see through the macro based approach.

…(SHT_GNU_versym) section

- Remove & properly handle unwrap in VersymIter::next
- Fix VersymIter::size_hint
- Adapt datatypes of fields in exposed ELF structs

- Remove calls to unwrap and validate offsets in all Iterator implementations
- Adapt datatypes of fields in exposed ELF structs

- Return 0 as lower bound in size_hint impls (better hint for corrupt
  ELFs)
- Verdef/Verdaux/Verneed/Vernaux Iterator: Start yielding None on the
  next call if there is no valid next index

… to exposed structs

- impl From<ElfVersym> for Versym
- remove '_ lifetime annotation on SectionHeader slice

- remove string tables from VerdefSection / VerneedSection