v0.8.43

What's Changed

• Fix #626: add cljs.core/exists? by @borkdude in #918
• Fix #919: :js-libs + refer + rename clashes with core var by @borkdude in #920
• Fix #906: merge-opts loses :features of previous context by @borkdude in #921
• Fix #923: check for duplicate keys in dynamic set of map literal by @borkdude in #924

Full Changelog: v0.8.41...v0.8.43