In \crossref{orchardkeycomponents}, do not allow construction of Orchard spending keys such that the corresponding internal incoming viewing key is 0 or ⊥. (This was already specified for the external incoming viewing key.) Similarly in \crossref{orchardfullviewingkeyencoding}, do not consider a decoded key valid if either its external or internal incoming viewing key would be 0 or ⊥.
In \crossref{orchardkeycomponents}, do not allow construction of Orchard
spending keys such that the corresponding internal incoming viewing key is 0
or ⊥. (This was already specified for the external incoming viewing key.)
Similarly in \crossref{orchardfullviewingkeyencoding}, do not consider a
decoded key valid if either its external or internal incoming viewing key
would be 0 or ⊥.

fixes #598

zcash/zips,zcash/zips,zcash/zips,zcash/zips