- separated DFrameBuffer from DCanvas.

This was a bad idea from the start and really only made sense with DirectDraw.
These days a FrameBuffer represents an abstract hardware canvas that shares nothing with a software canvas so having these classes linked together makes things needlessly complicated.
The software render buffer is now a canvas object owned by the FrameBuffer.

Note that this commit deactivates a few things in the software renderer, but from the looks of it none of those will be needed anymore if we set OpenGL 2 as minimum target.

src/v_video.cpp

@@ -605,8 +605,12 @@ DSimpleCanvas::~DSimpleCanvas ()
 //==========================================================================
 
 DFrameBuffer::DFrameBuffer (int width, int height, bool bgra)
-	: DCanvas (ViewportScaledWidth(width, height), ViewportScaledHeight(width, height), bgra)
+	//: DCanvas 
 {
+	Width = ViewportScaledWidth(width, height);
+	Height = ViewportScaledHeight(width, height);
+	Bgra = bgra;
+
 	LastMS = LastSec = FrameCount = LastCount = LastTic = 0;
 	Accel2D = false;
 
@@ -796,32 +800,6 @@ void FPaletteTester::MakeTexture()
 	CurTranslation = t;
 }
 
-//==========================================================================
-//
-// DFrameBuffer :: CopyFromBuff
-//
-// Copies pixels from main memory to video memory. This is only used by
-// DDrawFB.
-//
-//==========================================================================
-
-void DFrameBuffer::CopyFromBuff (uint8_t *src, int srcPitch, int width, int height, uint8_t *dest)
-{
-	if (Pitch == width && Pitch == Width && srcPitch == width)
-	{
-		memcpy (dest, src, Width * Height);
-	}
-	else
-	{
-		for (int y = 0; y < height; y++)
-		{
-			memcpy (dest, src, width);
-			dest += Pitch;
-			src += srcPitch;
-		}
-	}
-}
-
 //==========================================================================
 //
 // DFrameBuffer :: SetVSync