Integer types support in Blitter

The blitter now supports integer types. This means:
- It supports conversions to/from integer types from/to
  other already supported types.
- It supports integer to integer conversions without going
  to an intermediate float format.

Also added a Blitter::GetScale() function to avoid having
2 instances of the same switch statement in the code and
added the read/write utility functions. The final Blitter
code is not longer peppered with switch statements and is,
hopefully, easier to read that way.

Change-Id: I80de519aaaa768f8cedd98f97dc4414dda75bf54
Reviewed-on: https://swiftshader-review.googlesource.com/4113
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>

src/D3D9/Direct3DVolumeTexture9.cpp

diff --git a/src/D3D9/Direct3DVolumeTexture9.cpp b/src/D3D9/Direct3DVolumeTexture9.cpp
index 5372a2e..5633cc1 100644
--- a/src/D3D9/Direct3DVolumeTexture9.cpp
+++ b/src/D3D9/Direct3DVolumeTexture9.cpp
@@ -216,18 +216,7 @@
 
 					for(int i = 0; i < dWidth; i++)
 					{
-						sw::Color<float> color;
-
-						if(filter <= D3DTEXF_POINT)
-						{
-							color = source->readInternal((int)x, (int)y, (int)z);
-						}
-						else   // filter >= D3DTEXF_LINEAR
-						{
-							color = source->sampleInternal(x, y, z);
-						}
-
-						dest->writeInternal(i, j, k, color);
+						dest->copyInternal(source, i, j, k, x, y, z, filter > D3DTEXF_POINT);
 
 						x += w;
 					}