improve behavior of variable editor * main-window.cc (main_window::refresh_variable_editor): Call variable_editor_window::refresh, not variable_editor_window::clear_data_cache. * variable-editor-model.cc (cell::cell): Use default argument to merge two constructors. (variable_editor_model::impl): Use C++11 syntax to disable copying and default constructor. (variable_editor_model::data): Set pending state before posting event. (variable_editor_model::setData): Avoid flicker issue by temporarily setting data to string user entered. (variable_editor_model::set_data_oct): Use try-catch block to handle parsing and evaluation errors. Don't emit signals. (variable_editor_model::set_data_oct, variable_editor_model::set_data_oct, variable_editor_model::init_from_oct, variable_editor_model::eval_oct, variable_editor_model::retrieve_variable): Tag as a function that must be evaluated in the interpreter thread. * variable-editor.cc (variable_editor::refresh): New function.

--- a/libgui/src/main-window.cc	Mon Jan 22 01:31:53 2018 -0500
+++ b/libgui/src/main-window.cc	Sun Jan 21 10:39:19 2018 -0500
@@ -1751,7 +1751,7 @@
 void
 main_window::refresh_variable_editor (void)
 {
-  m_variable_editor_window->clear_data_cache ();
+  m_variable_editor_window->refresh ();
 }
 
 void