Add missing data member function in CwiseUnaryView
(transplanted from 05721eeefb9eb951d85ab799731517fbc5a8732c)

--HG--
branch : 3.1
extra : transplant_source : %05r%1E%EE%FB%9E%B9Q%D8Z%B7%99s%15%17%FB%C5%A8s%2C