v2.15.1: Oct 16 2025

### Regressions

- parser: Fix attribute normalization and standalone check

### Build

- io: Handle clashing error codes on AIX
- Fixed compilation error on GCC versions prior to 4.5 (Lars Erik Wik)
- meson: Fix install dir of man pages

### Deprecations

- tree: Undeprecate several struct members
- io: Undeprecate xmlOutputBuffer members
- valid: Undeprecate xmlValidGetPotentialChildren