SDL:Update XPM icon

See merge request !441

GCC8: Disable multi statement macros errors.

See merge request !459

Fix rendering gaps on polys with upper/lower textures

See merge request !453

Disable the APNG code if the version of libpng is greater than 1.4.

See merge request !457

Since supposedly the current code *can't* work with newer versions of libpng that have the apng patch, it won't compile if that's what people have.
It seems like some distros are adding the apng patch to libpng and that'll make things annoying to compile for people.
I think it goes without saying, but if there's ever a fix to make newer libpng versions work with the APNG code then this can be reverted.

Resolve buffer overflow crash when configuring System Menu and GIF controls

See merge request !445

Update capslock state on window re-focus

See merge request !436

Make AppVeyor installer paths consistent with Travis installer paths

See merge request !446

Make AppVeyor installer paths consistent with Travis installer paths(assets/deployer/installer -> assets/installer)

MinGW64:Target nocona for 64-bit builds [revision]

See merge request !440

Add 64-bit job to Appveyor

See merge request !442

Add Windows installer building to AppVeyor

See merge request !443

ARM and ARM64 support with MSVC toolchain

See merge request STJr/SRB2!412

Update code versions to 2.1.23

See merge request !435

Hide SRB2-CHAT behind #ifndef NONET

See merge request !434