QTads 3.1

• Fixed sound not working correctly anymore after canceling a sound with a
  crossfade.

• Fixed a Unicode parsing issue that could result in broken text matching due
  to miscompilation on some systems resulting from C++ undefined behavior.
  This could have all sorts of weird side effects, like verbs, nouns, etc,
  not getting recognized, HTML tags not working, and anything in-between.

• Fixed lower-case conversion assuming the text is always UTF-8, even though
  this is usually not true in Tads 2 games. This could in some cases cause
  issues for non-ASCII Tads 2 games. Now the proper text codec is used.

• Fixed "unnamed" (from the point of view of Tads) temporary files being
  created in the OS root directory (and thus usually failing since the user
  doesn't have filesystem permission to write there.) Now those files will be
  created in the proper, OS-configured directory for temp files.

• Various bugfixes in the audio engine. Due to this, FluidSynth 2.x is now
  required for MIDI support. Ubuntu 20.04 ships it. 18.04 does not.

• The Linux AppImage binary had a broken online update check on some systems.
  This was due to an incompatibility caused by the AppImage bundling a copy
  of OpenSSL 1.0 (from Ubuntu 16.04) and using that copy unconditionally.
  We now bundle 1.1 but don't use it if the system already provides it. We
  only use it on old distros that only provide OpenSSL 1.0. This is necessary
  because 1.0 and 1.1 are incompatibile with each other; an application built
  using 1.1 won't run with 1.0 and vice versa.

• A C++17 compiler is now required. GCC 5.4 (Ubuntu 16.04) is the oldest GCC
  version that is verified to still be able to build QTads.