maint: Use C++11 nullptr rather than 0 or NULL when possible. * FigureWindow.h, Logger.cc, Menu.cc, MouseModeActionGroup.h, Object.h, ObjectFactory.cc, ObjectProxy.h, color-picker.h, documentation-dock-widget.h, files-dock-widget.h, find-files-dialog.h, history-dock-widget.h, file-editor-tab.cc, file-editor.cc, file-editor.h, find-dialog.h, main-window.cc, main-window.h, octave-dock-widget.h, parser.cc, parser.h, webinfo.h, resource-manager.cc, shortcut-manager.cc, shortcut-manager.h, terminal-dock-widget.h, welcome-wizard.cc, welcome-wizard.h, workspace-model.h, workspace-view.h, __magick_read__.cc, call-stack.cc, call-stack.h, cdisplay.c, display.cc, dlmread.cc, dynamic-ld.cc, ft-text-renderer.cc, gl2ps-print.cc, graphics.cc, graphics.in.h, input.h, interpreter.cc, interpreter.h, ls-hdf5.cc, mex.cc, mxarray.in.h, oct-errno.in.cc, oct-fstrm.cc, oct-iostrm.h, oct-procbuf.cc, oct-stdstrm.h, oct-stream.cc, oct-stream.h, octave-link.cc, pager.cc, pr-output.cc, profiler.h, qz.cc, sighandlers.cc, strfns.cc, symtab.cc, symtab.h, typecast.cc, urlwrite.cc, variables.cc, __eigs__.cc, __init_fltk__.cc, __ode15__.cc, colamd.cc, ov-base-int.cc, ov-base.cc, ov-bool-mat.cc, ov-bool-sparse.cc, ov-builtin.cc, ov-class.cc, ov-classdef.cc, ov-complex.cc, ov-cx-diag.cc, ov-cx-mat.cc, ov-cx-sparse.cc, ov-fcn-handle.cc, ov-fcn-inline.cc, ov-flt-complex.cc, ov-flt-cx-diag.cc, ov-flt-cx-mat.cc, ov-flt-re-diag.cc, ov-flt-re-mat.cc, ov-java.cc, ov-java.h, ov-lazy-idx.cc, ov-perm.cc, ov-range.cc, ov-re-diag.cc, ov-re-mat.cc, ov-re-sparse.cc, ov-str-mat.cc, ov-struct.cc, ov-usr-fcn.h, octave.cc, octave.h, bp-table.cc, jit-ir.cc, jit-ir.h, jit-typeinfo.cc, jit-typeinfo.h, lex.h, pt-arg-list.cc, pt-arg-list.h, pt-array-list.h, pt-cell.h, pt-classdef.h, pt-colon.cc, pt-decl.h, pt-eval.cc, pt-eval.h, pt-except.h, pt-idx.h, pt-jit.cc, pt-jit.h, pt-loop.h, pt-mat.h, pt-select.h, pt.h, CSparse.cc, dSparse.cc, DASPK.cc, DASRT.cc, DASSL.cc, oct-fftw.cc, oct-rand.cc, oct-spparms.cc, child-list.cc, file-ops.cc, mach-info.cc, oct-env.cc, oct-time.cc, cmd-edit.cc, cmd-hist.cc, oct-locbuf.cc, oct-shlib.cc, pathsearch.cc, singleton-cleanup.cc, unwind-prot.h, url-transfer.cc: Use C++11 nullptr rather than 0 or NULL when possible.

--- a/libinterp/parse-tree/lex.h	Fri Apr 28 15:29:39 2017 -0400
+++ b/libinterp/parse-tree/lex.h	Fri Apr 28 13:19:12 2017 -0700
@@ -546,7 +546,7 @@
       octave_comment_list *comment_list;
     };
 
-    base_lexer (interpreter *interp_context = 0)
+    base_lexer (interpreter *interp_context = nullptr)
       : lexical_feedback (), scanner (0), input_buf (), comment_buf (),
         m_interp_context (interp_context)
     {
@@ -700,7 +700,7 @@
 
     int handle_token (const std::string& name, int tok);
 
-    int handle_token (int tok, token *tok_val = 0);
+    int handle_token (int tok, token *tok_val = nullptr);
 
     int count_token (int tok);
 
@@ -720,16 +720,16 @@
   {
   public:
 
-    lexer (interpreter *interp_context = 0)
+    lexer (interpreter *interp_context = nullptr)
       : base_lexer (interp_context), reader (this)
     { }
 
-    lexer (FILE *file, interpreter *interp_context = 0)
+    lexer (FILE *file, interpreter *interp_context = nullptr)
       : base_lexer (interp_context), reader (file, this)
     { }
 
     lexer (const std::string& eval_string,
-           interpreter *interp_context = 0)
+           interpreter *interp_context = nullptr)
       : base_lexer (interp_context), reader (eval_string, this)
     { }
 
@@ -784,27 +784,27 @@
   {
   public:
 
-    push_lexer (interpreter *interp_context = 0)
+    push_lexer (interpreter *interp_context = nullptr)
       : base_lexer (interp_context), pflag (1)
     {
       append_input ("", false);
     }
 
     push_lexer (const std::string& input,
-                interpreter *interp_context = 0)
+                interpreter *interp_context = nullptr)
       : base_lexer (interp_context), pflag (1)
     {
       append_input (input, false);
     }
 
-    push_lexer (bool eof, interpreter *interp_context = 0)
+    push_lexer (bool eof, interpreter *interp_context = nullptr)
       : base_lexer (interp_context), pflag (1)
     {
       append_input ("", eof);
     }
 
     push_lexer (const std::string& input, bool eof,
-                interpreter *interp_context = 0)
+                interpreter *interp_context = nullptr)
       : base_lexer (interp_context), pflag (1)
     {
       append_input (input, eof);