Make sure sprite colors in the editor don't update more than 30 FPS

This adds Graphics::crewcolourreal(), which is like the
entityclass::crewcolour() that the editor already uses, except for the
real color instead of the color ID. Also, editorclass now has an
attribute `entcolreal` so enemy colors don't update more than 30 frames
a second.

desktop_version/src/Graphics.cpp

@@ -3080,3 +3080,23 @@ void Graphics::reloadresources() {
 
 	music.init();
 }
+
+Uint32 Graphics::crewcolourreal(int t)
+{
+	switch (t)
+	{
+	case 0:
+		return col_crewcyan;
+	case 1:
+		return col_crewpurple;
+	case 2:
+		return col_crewyellow;
+	case 3:
+		return col_crewred;
+	case 4:
+		return col_crewgreen;
+	case 5:
+		return col_crewblue;
+	}
+	return col_crewcyan;
+}