WebPIoInitFromOptions: treat use_cropping as a bool
WebPIoInitFromOptions: treat use_cropping as a bool

this matches the description in WebPDecoderOptions and prevents a
mismatch between the user supplied options and the ones used by io.

Bug: chromium:1196480
Change-Id: Id464f999d737078078f9d21afe25b349317f5ab4

PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp