Detection of inline namespaces is imperfect as some compilers
don't provide __has_feature

This option allows to override it if needed.

* added position independent documentation

* suggested fixes to usage

* linebreaks
Co-authored-by: Adnan Yunus <adnan@opus.ai>

Co-authored-by: darklukee <no-reply@hidden>

Co-authored-by: Bart Siwek <bsiwek@cisco.com>