refactor(sonar): clean up issues reported on PR 209

- remove locals left unused after the dead-store cleanup (cpp:S1481, cpp:S1854)
- unnamed unused parameter (cpp:S1172)
- single-use declarations moved into if init-statements (cpp:S6004)
- auto for casted initialisers (cpp:S5827)
- const references and pointers where nothing is modified (cpp:S5350)
- rename structured bindings shadowed by inner declarations (cpp:S1117)

gl/vao.cpp

@@ -60,7 +60,7 @@ void gl::vao::bind()
 		glBindVertexArray(*this);
 	}
 	else {
-		for (attrib_params &param : params) {
+		for (attrib_params const &param : params) {
 			param.buffer.bind(gl::buffer::ARRAY_BUFFER);
 			glVertexAttribPointer(param.attrib, param.size, param.type, GL_FALSE, param.stride, reinterpret_cast<void*>(param.offset));
 			glEnableVertexAttribArray(param.attrib);