Add: Option to (dis-)allow accelerated video drivers. (#8819)

The video drivers using the OpenGL backend are currently our only
accelerated drivers. The options defaults to off for macOS builds and
to on everywhere else.

Co-authored-by: Michael Lutz <michi@icosahedron.de>

src/video/video_driver.cpp

@@ -17,6 +17,8 @@
 #include "../window_func.h"
 #include "video_driver.hpp"
 
+bool _video_hw_accel; ///< Whether to consider hardware accelerated video drivers.
+
 bool VideoDriver::Tick()
 {
 	auto cur_ticks = std::chrono::steady_clock::now();