Fixed Windows warnings

- Removed unused variables
- Removed unreachable code
- Fixed size_t <-> int conversions
- Fixed uninitialized variables

Change-Id: Ifc3912e92b8f0710094e939bd0da4757148b559a
Reviewed-on: https://swiftshader-review.googlesource.com/5681
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
diff --git a/src/Shader/PixelPipeline.cpp b/src/Shader/PixelPipeline.cpp
index e353c27..5987768 100644
--- a/src/Shader/PixelPipeline.cpp
+++ b/src/Shader/PixelPipeline.cpp
@@ -378,9 +378,9 @@
 
 	void PixelPipeline::blendTexture(Vector4s &temp, Vector4s &texture, int stage)
 	{
-		Vector4s *arg1;
-		Vector4s *arg2;
-		Vector4s *arg3;
+		Vector4s *arg1 = nullptr;
+		Vector4s *arg2 = nullptr;
+		Vector4s *arg3 = nullptr;
 		Vector4s res;
 
 		Vector4s constant;