Slight performance issue with moving clouds background

[christopho]

Bug report from polyphagia on IRC, ZSDX 1.10.1:

<polyphagia> just started zsdx and the game had a bit of slowdown behind some castle to the east with moving clouds in the background 
<polyphagia> and that was the first and only time i experienced it 
<christopho> ok, you have that with the latest version? 
<polyphagia> whatever is in the debian repo 
<polyphagia> it's not serious at all, i'm being pedantic 
<polyphagia> but it was noticeable