Fixed signed/unsigned types comparison

BUG=18368388

Change-Id: I3f2927fd68e75a8fb5abde1b25e81416862076fc
Reviewed-on: https://swiftshader-review.googlesource.com/1474
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/Renderer/Renderer.cpp

diff --git a/src/Renderer/Renderer.cpp b/src/Renderer/Renderer.cpp
index 27ef798..290322a 100644
--- a/src/Renderer/Renderer.cpp
+++ b/src/Renderer/Renderer.cpp
@@ -1905,7 +1905,7 @@
 
 		size_t count = vertexShader->getLength();
 
-		for(int i = 0; i < count; i++)
+		for(size_t i = 0; i < count; i++)
 		{
 			const Shader::Instruction *instruction = vertexShader->getInstruction(i);
 
@@ -1949,7 +1949,7 @@
 
 		size_t count = pixelShader->getLength();
 
-		for(int i = 0; i < count; i++)
+		for(size_t i = 0; i < count; i++)
 		{
 			const Shader::Instruction *instruction = pixelShader->getInstruction(i);