Store X value (time) for all graph entries in addition to the Y value (FPS, prediction margin etc.). The `CGraph::Add` function adds values to the graph at the current time. The `CGraph::InsertAt` function allows specifying arbitrary X values, as long as the values are inserted in increasing order.
The entries are kept in a ringbuffer and old entries are recycled when it's full. The size of the ringbuffer is configurable for each graph, as the FPS graph needs significantly more buffer because values are added more often.
The scrolling speed of the graphs is fixed by specifying the maximum size of the window of values which should be displayed. For this purpose, a parameter is added to the `CGraph::Scale` function to specify the size of the window which should be rendered in the `CGraph::Render` function. For the FPS graph only the last second is rendered, so small spikes are still noticeable. For prediction and gametime margin graphs the last five seconds are rendered, which should result in a similar scrolling speed as before this change. The debug tuning graph is a special case, where the X values set manually and fixed to 0-127, same as before, instead of being based on the current time.
The graph rendering is made much more efficient by precalculating when the vertex colors need to be updated, to avoid all unnecessary calls to `SetColorVertex`. Additionally, line items are bundled together in an array to avoid calling `LinesDraw` for every individual line item.
