Make error messages more specific about the variable and problem encountered. * besselj.cc, bitfcns.cc, colloc.cc, daspk.cc, dasrt.cc, dassl.cc, data.cc, dirfns.cc, ellipj.cc, error.cc, gl-render.cc, graphics.cc, graphics.in.h, load-path.cc, lsode.cc, lu.cc, luinc.cc, oct-hist.cc, oct-obj.cc, octave-link.cc, quad.cc, rand.cc, symtab.cc, sysdep.cc, toplev.cc, utils.cc, variables.cc, __init_fltk__.cc, chol.cc, fftw.cc, ov-cell.cc, ov-ch-mat.cc, ov-class.cc, ov-classdef.cc, ov-cx-mat.cc, ov-fcn-inline.cc, ov-struct.cc, ov-usr-fcn.cc, CMatrix.cc, dMatrix.cc, fCMatrix.cc, fMatrix.cc, lo-specfun.cc, curl.m, divergence.m, __fltk_file_filter__.m, __uiobject_split_args__.m, uigetfile.m, doc.m, imshow.m, rref.m, subspace.m, edit.m, fileattrib.m, open.m, substruct.m, annotation.m, axis.m, caxis.m, datetick.m, hidden.m, legend.m, whitebg.m, colorbar.m, __add_datasource__.m, __ezplot__.m, __pie__.m, __plt_get_axis_arg__.m, pan.m, __print_parse_opts__.m, rotate3d.m, subplot.m, zoom.m, compan.m, addpref.m, getpref.m, setpref.m, powerset.m, bicg.m, bicgstab.m, cgs.m, qmr.m, spaugment.m, pascal.m, moment.m, cstrcat.m, system.tst: Make error messages more specific about the variable and problem encountered.

--- a/scripts/plot/appearance/datetick.m	Tue Nov 17 22:04:42 2015 +0100
+++ b/scripts/plot/appearance/datetick.m	Wed Nov 18 10:40:26 2015 -0800
@@ -132,10 +132,10 @@
   if (! isempty (form))
     if (isnumeric (form))
       if (! isscalar (form) || form < 0 || form != fix (form))
-        error ("datetick: expecting FORM argument to be a positive integer");
+        error ("datetick: FORM argument must be a positive integer");
       endif
     elseif (! ischar (form))
-      error ("datetick: expecting valid date format string");
+      error ("datetick: FORM argument must be a valid date format string");
     endif
   endif