Check if all Elements of x are zero.
Check if x is a power of 2 (binary power). See also: http://forum.dlang.org/thread/zumhmosfkvwjymjhmtlt@forum.dlang.org#post-fvnmurrctavpfkunssdf:40forum.dlang.org
Return true if x is a equal to any of ys. TODO Make ys lazy if any of ys is a delegate. TODO Reuse among
Return true if x is a equal to any of ys. TODO Reuse among
Predicate extensions to std.algorithm.