[cff, type1] Sanitize `BlueFuzz' and `BlueShift'.

Reported as

  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=7371

* src/cff/cffload.c (cff_load_private_dict): Sanitize
`priv->blue_shift' and `priv->blue_fuzz' to avoid overflows later
on.

* src/type1/t1load.c (T1_Open_Face): Ditto.