Release v0.1.1

This is a minor bug fix release, to solve some issues that arose while
integrating libplacebo into VLC 3.0.

Fixes:
- various fixes under NDEBUG
- removed the LIBPLACEBO_ENABLE_SECURITY_BUGS nag under NDEBUG
- removed the LIBPLACEBO_LEAK_REPORT check under NDEBUG
This tag has no release notes.