[all] add initial support for RGB24-bpp support #2377

Job	Run time
host-windows-cross	58s
host-linux	32s
client (gcc, g++, xdg-shell, Release)	40s
docs	42s
client (gcc, g++, xdg-shell, Debug)	47s
host-windows-native	1m 24s
module	16s
client (gcc, g++, libdecor, Release)	56s
obs (gcc)	46s
client (gcc, g++, libdecor, Debug)	51s
obs (clang)	1m 13s
client (clang, clang++, xdg-shell, Release)	1m 3s
client (clang, clang++, xdg-shell, Debug)	1m 19s
client (clang, clang++, libdecor, Release)	1m 6s
client (clang, clang++, libdecor, Debug)	42s
	13m 15s

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