m_xrr_config was used by the GeneralWidget::GetAvailableResolutions
function to get the list of supported fullscreen resolutions when
HAVE_XRANDR was set. aa4088a removed the ability to set that resolution
in the UI, leaving the GetAvailableResolutions function unused.
m_xrr_config is initialized in MainWindow which still uses it to toggle
fullscreen, but the references in GeneralWidget and GraphicsWidget
(which just ferried m_xrr_config from MainWindow to GeneralWidget) are
now unnecessary and removed in this commit.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
Pokechu22