static_cast<T const> and const_cast<T const> are meaningless when T is
not a class type, because the result is a prvalue and prvalues of
non-class type are unqualified. I'm removing these pointless
const-qualifications now, because I'm experimenting with a patch to
make the front-end warn about this.

	* include/ext/pb_ds/detail/list_update_map_/iterators_fn_imps.hpp
	(PB_DS_CLASS_C_DEC::end()): Remove redundant const in cast type.
	* testsuite/util/testsuite_rng.h (twister_rand_gen::get_prob()):
	Likewise.

Tested powerpc64le-linux, committed to trunk.