Fixed pow(), and added finite(), isinf(), and isnan(). Also fixed

Fixed pow(), and added finite(), isinf(), and isnan(). Also fixed
pow() tests.
@- Fixed pow(), and added finite(), isinf(), and isnan(). (Jim)
# Jeroen was on crack, and apparently flunked arithmetic. Names of new
# functions subject to change if people get persnickety about them.
# (They're currently the same as the underlying C library function
# names. Hope nobody forgets to update the tests if they change the
# names.)
# Oh, and pow() uses the new parameter-passing API now.