add heix support to README

increase version number to v1.6.1

Merge branch 'master' of github.com:strukturag/libheif

Detect non-existing referenced alpha images (fixes strukturag#123) / C…

…VE-2019-11471

Merge pull request strukturag#148 from strukturag/fix-go-races

CI: Run race tester as part of Travis GO job.

Fix cmake build on Windows.

Introduced in e6ecace

show in configure summary whether we compile gdkpixbuf2 loader

increase version to v1.3.2, libtool version 4:2:3

increase version to v1.3.1, libtool version 4:1:3

increase version to v1.3.0, libtool version 4:0:3