allow list literals with a constant multiplier to be assigned to C arrays, extend array assignment tests
avoid duplication of "stringsource" entries in filename table

--HG--
extra : amend_source : c0a1e78dbfd443585a80bd646b763617eeb6b7c5
fix a case where C array coercion helper code could be duplicated in the C file
speed up cythonized hexiom2 benchmark a little by using C int arrays instead of fixed size Python lists