rescaler: harmonize function protos
rescaler: harmonize function protos

Change-Id: I13b5f9add83c1225c82a650f3ef717582b057247

webmproject/libwebp,ttyangf/libwebp,Aexyn/libwebp,ttyangf/libwebp,Aexyn/libwebp,ttyangf/libwebp,redengineer/libwebp,yohunl/libwebp,PKRoma/libwebp,webmproject/libwebp,ttyangf/libwebp,webmproject/libwebp,Aexyn/libwebp,redengineer/libwebp,yohunl/libwebp,yohunl/libwebp,yohunl/libwebp,redengineer/libwebp,PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,Aexyn/libwebp,Aexyn/libwebp,yohunl/libwebp,ttyangf/libwebp,redengineer/libwebp,PKRoma/libwebp,redengineer/libwebp,webmproject/libwebp