primitive rendering now implemented for stretched H2xE; removed the old implementation of SL(2,R)

shaders.cpp

@@ -359,6 +359,7 @@ void display_data::set_projection(int ed) {
   
   if(selected->uIterations != -1) {
     glhr::set_index_sl(0);
+    glhr::set_sv(stretch::not_squared());
     glhr::set_sl_iterations(slr::steps);
     }