Fix non const data() member in Array and Matrix wrappers.
(transplanted from 004fdfaa585e209523ee072616b5cd40192caf56)

--HG--
branch : 3.1
extra : transplant_source : %00O%DF%AAX%5E%20%95%23%EE%07%26%16%B5%CD%40%19%2C%AFV