Fix errors and warnings

Former-commit-id: a3ba309633f198f82c1d0277d750d867cad4ba44

src/Nazara/Core/String.cpp

@@ -1912,7 +1912,6 @@ namespace Nz
 		}
 		else
 		{
-			unsigned int newSize = m_sharedString->size + length;
 			auto newString = std::make_shared<SharedString>(m_sharedString->size + length);
 
 			char* ptr = newString->string.get();