Lataa uTox 0.18.1

Fixes:
- Solved crash when undoing chat input with ctrl-z (@siburec) ()
- groups: load group topics from Tox save ()
- Fix heap-use-after-free when creating new group chats (@siburec) ()
- langs: Remove strings that are not supposed to be translated ()
- Use correct type for pthread entry point (@krobelus) ()
- Pass enum value with correct type when cancelling file transfers (@krobelus) ()
- Copy text from chat without nicks via ctrl-c in Windows (@redmanmale) ()
Documentation:
- README.md: Add Spanish to the list of complete translations ()
- Add Debian installation instructions (@garetethan) ()
- docs: fix simple typo, precomplied -> precompiled (@timgates42) ()
Languages:
- Complete Spanish translation (@siburec) ()
Development:
- edit_do(): rename variable new to new_change ()
- edit_do(): remove useless variable history ()
- CI cleanup:
- add tools/timediff.py ()
- CI: OSX: Don't cleanup after installing with brew ()
- CI: OSX: Don't brew update ()
- CI: OSX: Install opus and lib{vpx,sodium} from brew ()
- CI: Win64: Don't install libopenal, it's already being compiled ()
- CI: Linux: Install lib{sodium,opus,vpx}-dev from repo ()
- rm extra/common/build_openal.sh ()
- Port Travis configuration to GitHub Actions (@krobelus) ()
- Disable -Werror for 3rd party projects (@krobelus) ()
- Require libsodium only when linking statically ()
- Remove libsodium dependency ()
- travis.yml: update OS to "focal" (latest) ()