Fix a shitloads of warnings on VS

Former-commit-id: fca61118f4e0530ed2eaaf9ff96de29806aa5aa8

include/Nazara/Core/StringStream.hpp

@@ -50,7 +50,7 @@ namespace Nz
 
 		private:
 			std::vector<String> m_strings;
-			unsigned int m_bufferSize;
+			std::size_t m_bufferSize;
 	};
 }