v1.8.3 - PSP CISO crash fix

Bug fixes:

• Fix a division by zero when reading PSP CISO/CSO images.
  • This bug was reported by @NotaInutilis in issue #286.
• Fix a crash in the BC7 and PVRTC image decoders if the image dimensions were not a multiple of the tile size.
• rp-download: Allow clone3(), which is needed on systems that have by glibc-2.34.

Other changes:

• GTK+ frontends now use libgsound if available.
• Experimental support for GTK4 has been added. It's not available by default (configuration is commented out in CMake), since none of the major file browsers support GTK4 yet.

Ubuntu packages are available from an Ubuntu PPA for Ubuntu 16.04 "Xenial" Xerus, Ubuntu 18.04 "Bionic" Beaver, Ubuntu 20.04 "Focal" Fossa, and Ubuntu 21.04 "Hirsute" Hippo.

To add the PPA and install rom-properties, run the following commands:

sudo add-apt-repository ppa:gerbilsoft/ppa
sudo apt-get update
sudo apt-get install rom-properties-all

This will install all rom-properties frontends and executables. Individual frontends can be installed by installing the relevant rom-properties-* package.