libwebp: Use ExUtilGet*() in anim_diff
libwebp: Use ExUtilGet*() in anim_diff

Instead of strtod() or strtol().

Change-Id: I320373cd969c6969cf4b1491391a95668d1b0beb

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