doc-src/Tutorial/Ifexpr/norm

HOL/record: shared operations ("more", "fields", etc.) now need to be
always qualified;

consts norm :: ifex => ifex
primrec
"norm (CIF b)    = CIF b"
"norm (VIF x)    = VIF x"
"norm (IF b t e) = normif b (norm t) (norm e)"