maint: Deprecate is_empty and replace with isempty. * ov.h (is_empty): Use OCTAVE_DEPRECATED macro around function. * ov.h (isempty): New function. * Array.h (is_empty): Use OCTAVE_DEPRECATED macro around function. * Array.h (isempty): New function. * Range.h (is_empty): Use OCTAVE_DEPRECATED macro around function. * Range.h (isempty): New function. * Sparse.h (is_empty): Use OCTAVE_DEPRECATED macro around function. * Sparse.h (isempty): New function. * Backend.cc, BaseControl.cc, Canvas.cc, Figure.cc, gl-select.cc, __magick_read__.cc, __qp__.cc, cellfun.cc, daspk.cc, dasrt.cc, dassl.cc, data.cc, debug.cc, det.cc, eig.cc, error.cc, fft.cc, filter.cc, find.cc, ft-text-renderer.cc, gl-render.cc, gl2ps-print.cc, graphics.cc, graphics.in.h, hess.cc, inv.cc, lsode.cc, lu.cc, max.cc, mex.cc, mxarray.in.h, oct-handle.h, oct-lvalue.cc, oct-map.cc, oct-map.h, oct-stream.cc, pinv.cc, pr-output.cc, quadcc.cc, qz.cc, strfind.cc, strfns.cc, sylvester.cc, time.cc, toplev.cc, tril.cc, urlwrite.cc, utils.cc, utils.h, xnorm.cc, __delaunayn__.cc, __glpk__.cc, __init_fltk__.cc, __init_gnuplot__.cc, __ode15__.cc, __voronoi__.cc, chol.cc, convhulln.cc, ov-base-diag.cc, ov-base-mat.cc, ov-base-sparse.cc, ov-base.cc, ov-base.h, ov-bool-mat.cc, ov-bool-sparse.cc, ov-cell.cc, ov-class.cc, ov-classdef.cc, ov-cx-sparse.cc, ov-fcn-inline.cc, ov-flt-re-mat.cc, ov-intx.h, ov-java.cc, ov-perm.cc, ov-range.cc, ov-re-mat.cc, ov-re-sparse.cc, ov-str-mat.cc, ov-struct.cc, ov-usr-fcn.cc, ov.cc, ov.h, bp-table.cc, oct-parse.in.yy, pt-eval.cc, pt-tm-const.cc, pt-tm-const.h, Array.cc, Range.cc, Range.h, Sparse.cc, Sparse.h, chNDArray.cc, dNDArray.cc, fNDArray.cc, DASPK.cc, DASRT.cc, DASSL.cc, LSODE.cc, bsxfun-defs.cc, eigs-base.cc, oct-convn.cc, qr.cc: Replace instances of is_empty with isempty.

--- a/libinterp/corefcn/quadcc.cc	Sun Jun 11 15:35:21 2017 -0700
+++ b/libinterp/corefcn/quadcc.cc	Sun Jun 11 22:14:09 2017 -0700
@@ -1602,7 +1602,7 @@
   else
     b = args(2).double_value ();
 
-  if (nargin < 4 || args(3).is_empty ())
+  if (nargin < 4 || args(3).isempty ())
     tol = 1.0e-6;
   else if (! args(3).is_real_scalar () || args(3).double_value () <= 0)
     error ("quadcc: tolerance (TOL) must be a single real scalar > 0");