single-pixel-buffer: new protocol

This protocol allows creating single-pixel buffers. It can be useful
to avoid having to allocate a real buffer just to fill it with the
same pixel value. Some use-cases include drawing background surfaces
or toplevel decorations.

Signed-off-by: Simon Ser <contact@emersion.fr>
3 jobs for solid-color-buffer in 44 seconds
Name Stage Failure
failed
test-meson Test
meson.build:71:2: ERROR: Problem encountered: Missing README in staging/solid-buffer/solid-buffer-v1.xml

A full log can be found at /builds/emersion/wayland-protocols/build/meson-logs/meson-log.txt
Uploading artifacts for failed job
Uploading artifacts...
/builds/emersion/wayland-protocols/build/meson-logs: found 2 matching files and directories

Uploading artifacts as "archive" to coordinator... 201 Created
id=22190305 responseStatus=201 Created token=BsJhyX7T
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1