
This function calculates values of its arguments, from left to right.
If the value of calculated parameter is false, the function returns false immediately,
without calculating of the remaining parameters.
If the lsit of arguments ends without any false value calculated, the function
returns true (Thus it will return true if called without arguments).

The name of this function is the same as name of "and" XPATH and XQUERY operator.
Thus it must be surronded bu double quotes when used in XPATH or XQUERY expressions.
Moreover, this function is not a part of XPATH standard, so it cannot be used if
portability is important.
