Add support for right-aligned roomtext

This is mostly so people making levels in an RTL language have a more
pleasant and logical experience. If roomtext is placed in a level set
to RTL, it will get p1=1, which makes that roomtext right-aligned.
Because, imagine for English you click to place roomtext, and the text
runs left of where you clicked, which wouldn't be logical.

Since it's an entity-bound property, switching RTL on and off either in
the editor or via a script does not affect existing entities.

desktop_version/src/Map.cpp

@@ -1895,6 +1895,7 @@ void mapclass::loadlevel(int rx, int ry)
                 text.x = ex / 8;
                 text.y = ey / 8;
                 text.text = ent.scriptname.c_str();
+                text.rtl = ent.p1;
                 roomtext.push_back(text);
                 break;
             }