This fixes a memory leak that would occur when the Android frontend
calls LogManager::Init more than once in order to reload settings.

Note that the log window listener is now owned by LogManager instead of
by the frontend, making it consistent with the other log listeners.

qOverload is used to disambiguate pointers to overloaded functions, but
most of the usages in the code base were with non-overloaded functions.

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.

This should give us a nicer font on Windows, while also not severely
impacting the existing behavior on Linux.

Provides the same behvaior, but in a much more concise manner.

moving a temporary object prevents copy elision. Remove std::move.

Otherwise, a line that's too wide for the log widget will cause the horizontal scroll bar to appear, which reduces the vertical height, and causes the most recent line to be off screen.  Since that line is off screen, the log widget no longer scrolls as new lines appear, unless it's manually scrolled to the very bottom again.