The binary operators and function xor can now combine any is.booltype vectors.
They now recycle if vectors have different length. If the two arguments have different booltypes the return value corresponds to the lower booltype of the two.
Boolean operations on bit vectors are extremely fast because they are
implemented using C's bitwise operators. Boolean operations on or bitwhich
vectors are even faster, if they represent very skewed selections.
The xor function has been made generic and xor.default has
been implemented much faster than R's standard xor.
This was possible because actually boolean function xor and
comparison operator != do the same (even with NAs), and != is
much faster than the multiple calls in (x | y) & !(x & y)