More warnings fixed

Fixed warnings related to type conversions leading to potential loss of precision.

BUG=18368388

Change-Id: I71a7941df4bcf991f04818060780d4d395e335a9
Reviewed-on: https://swiftshader-review.googlesource.com/1393
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/Shader/Shader.cpp

diff --git a/src/Shader/Shader.cpp b/src/Shader/Shader.cpp
index da0a84f..fc98eb5 100644
--- a/src/Shader/Shader.cpp
+++ b/src/Shader/Shader.cpp
@@ -1327,7 +1327,7 @@
 		return serialID;
 	}
 
-	int Shader::getLength() const
+	size_t Shader::getLength() const
 	{
 		return instruction.size();
 	}

src/Shader/Shader.hpp

diff --git a/src/Shader/Shader.hpp b/src/Shader/Shader.hpp
index 6486ed9..870f701 100644
--- a/src/Shader/Shader.hpp
+++ b/src/Shader/Shader.hpp
@@ -477,7 +477,7 @@
 		~Shader();

 

 		int getSerialID() const;

-		int getLength() const;

+		size_t getLength() const;

 		ShaderType getShaderType() const;

 		unsigned short getVersion() const;