devel/deheader: update to 1.12
Changes:
- Fixed typo in hsearch() pattern.
- Added requirements for entire SUSv2 coverage.
- Spellchecked the documentation.
- Corrected an error in CMake build detection.
- Typo fixes and code hardening by ChatGPT 5.2.
- Don’t over-remove duplicates when -r is specified.