Shader cleanup

A couple of class members from PixelShader and VertexShader
were still public. Fixed that in this cleanup.

Change-Id: I2dfaac7fd4cecdc791f1ef7236148e74c4b5b486
Reviewed-on: https://swiftshader-review.googlesource.com/5850
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>

src/Renderer/Renderer.cpp

diff --git a/src/Renderer/Renderer.cpp b/src/Renderer/Renderer.cpp
index d854deb..38b19ec 100644
--- a/src/Renderer/Renderer.cpp
+++ b/src/Renderer/Renderer.cpp
@@ -445,7 +445,7 @@
 					draw->vsDirtyConstB = 0;
 				}
 
-				if(context->vertexShader->instanceIdDeclared)
+				if(context->vertexShader->isInstanceIdDeclared())
 				{
 					data->instanceID = context->instanceID;
 				}