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/error.cc	Sun Jun 11 15:35:21 2017 -0700
+++ b/libinterp/corefcn/error.cc	Sun Jun 11 22:14:09 2017 -0700
@@ -903,7 +903,7 @@
 {
   octave::execution_exception e = make_execution_exception ("error");
 
-  if (! stack.is_empty ()
+  if (! stack.isempty ()
       && ! (stack.contains ("file") && stack.contains ("name")
             && stack.contains ("line")))
     error ("rethrow: STACK struct must contain the fields 'file', 'name', and 'line'");
@@ -924,7 +924,7 @@
   else
     rethrow_error_1 (id.c_str (), "%s", tmp_msg.c_str ());
 
-  if (! stack.is_empty ())
+  if (! stack.isempty ())
     {
       std::ostringstream buf;
 
@@ -997,7 +997,7 @@
               if (! msg)
                 return retval;
             }
-          else if (arg.is_empty ())
+          else if (arg.isempty ())
             return retval;
         }
     }
@@ -1214,7 +1214,7 @@
   if (nargin == 1 && args(0).is_map ())
     {
       // empty struct is not an error.  return and resume calling function.
-      if (args(0).is_empty ())
+      if (args(0).isempty ())
         return retval;
 
       octave_scalar_map m = args(0).scalar_map_value ();
@@ -1906,7 +1906,7 @@
 
           if (new_err.contains ("stack"))
             {
-              if (new_err.getfield ("stack").is_empty ())
+              if (new_err.getfield ("stack").isempty ())
                 initialize_stack = true;
               else
                 {