isaxes.m: New function to determine if object is axes handle. * scripts/plot/isaxes.m: New function. * scripts/plot/module.mk: Add function to build system. * NEWS: Announce new function. * doc/interpreter/plot.txi: Add function to manual. * libinterp/corefcn/graphics.cc(Fishandle), scripts/plot/isfigure.m: Update seealso links to mention isaxes.

--- a/scripts/plot/isfigure.m
+++ b/scripts/plot/isfigure.m
@@ -23,7 +23,7 @@
 ## If @var{h} is a matrix then return a logical array which is true where
 ## the elements of @var{h} are figure graphics handles and false where
 ## they are not.
-## @seealso{ishandle}
+## @seealso{isaxes, ishandle}
 ## @end deftypefn
 
 ## Author: jwe