[liborigin] fixes and improvements recommended by cppcheck

Description

Fixes and improvements recommended by cppcheck:

• use const& for sibling iterators
• don't use std::str.c_str() where std::str is already enough
• fix out of bound access in notes[file_object_id] if file_object_id is equal to notes.size()

Conformity

• Changelog entry
• Unit tests
• Update INSTALL
• Downport
• Fixes:

When external dependencies are removed

• Reporting to ...