Merge branch 'master' into next

SRB2_Debug.props

SRB2_Release.props

SRB2_common.props

appveyor.yml

deployer/appveyor/deployer.bat

libs/SDL2/lib/ARM/SDL2.lib

libs/SDL2/lib/ARM64/SDL2.dll

libs/SDL2/lib/ARM64/SDL2.lib

libs/SDL2_mixer/lib/ARM/SDL2_mixer.lib

libs/SDL2_mixer/lib/ARM64/SDL2_mixer.dll

libs/SDL2_mixer/lib/ARM64/SDL2_mixer.lib

libs/libpng-src/projects/visualc10/.gitignore

libs/libpng-src/projects/visualc10/libpng.vcxproj

libs/zlib/projects/visualc10/.gitignore

libs/zlib/projects/visualc10/zlib.vcxproj

srb2-vc10.sln

src/Makefile

src/hardware/r_opengl/r_opengl-vc10.vcxproj

src/hardware/s_openal/s_openal-vc10.vcxproj

src/i_tcp.c