Switch to author's provided src tarball instead of GitHub auto-generated.
Changes since -rc1:
* Don't silently fall back to unencrypted client/core communication if certificate cannot be loaded
* Properly escape LDAP usernames to prevent injection or bypassing authentication
* Strip format codes in ignore list rules (this might affect pre-existing rules)
* Improve window handling under Wayland
* Update bundled iconsets and application icons
* Update default network and documentation to point to our new home Libera IRC (since Freenode killed itself)