nanmax, nanmin
--------------
Add out and keepdims keywords.

nanargmin, nanargmax
--------------------
A NanWarning is raised if an all NaN slice detected. For all such
slices np.iingo(np.intp).min is returned as the index value.

nansum
------
The keywords dtype, out, and keepdims are added.

A FutureWarning is raised, as in the future the mean of an empty
slice after NaN replacement will be 0 instead of the current NaN.

nanmean, nanvar, nanstd
-----------------------
For all, if the input array is of inexact type then the dtype and out
parameters must be of inexact type if specified.  That insures that NaNs
can be returned when appropriate.

The nanmean function detects empty slices after NaN replacement and
raises a NanWarning. NaN is returned as the value for all such slices.

The nanmean and nanstd functions detect degrees of freedom <= 0 after
NaN replacement and raise a NanWarning. NaN is returned as the value for
all such slices.