[Bf-committers] Updated Blender cloth air pressure patch

[panjz]

Hi,

I have updated the cloth air pressure patch (#30941) to make it work with latest Blender svn version (r55292). I also merged cloth sewing seams patch (#31269) to my patch, so I 
removed the spring length scaling factor (use negative value for cloth 
shrinking in #31269 instead). I don't know whether merge other people's patch to my patch is OK. If not, I'll remove it.