Don't reinitialize the symbol tree in OpenFile.

(We don't reinitialize the option database, so why should we reinitialize
the variables? Using a single global symbol tree we can again define
variables with -string "" on the command line.)

Box/Main.cpp

-// $Id: Main.cpp,v 1.50 2005-06-20 16:40:25 geuzaine Exp $
+// $Id: Main.cpp,v 1.51 2005-10-24 15:38:13 geuzaine Exp $
 //
 // Copyright (C) 1997-2005 C. Geuzaine, J.-F. Remacle
 //
@@ -86,13 +86,15 @@ int main(int argc, char *argv[])
 {
   ParUtil::Instance()->init(argc, argv);
 
+  InitSymbols();
+
+  Init_Mesh0(&M);
+
   Init_Options(0);
 
   if(argc < 2)
     Info(0, argv[0]);
 
-  Init_Mesh0(&M);
-
   // FIXME: could not make this work on IRIX
 #if !defined(__sgi__) 
   signal(SIGINT, Signal);

Common/CommandLine.cpp

-// $Id: CommandLine.cpp,v 1.65 2005-09-22 22:39:22 geuzaine Exp $
+// $Id: CommandLine.cpp,v 1.66 2005-10-24 15:38:13 geuzaine Exp $
 //
 // Copyright (C) 1997-2005 C. Geuzaine, J.-F. Remacle
 //
@@ -155,10 +155,6 @@ char *Get_BuildOptions(void)
 
 void Get_Options(int argc, char *argv[])
 {
-  // This symbol context is local to option parsing (the symbols will
-  // not interfere with subsequent OpenFiles)
-  InitSymbols();
-
   // Parse session and option files
   ParseFile(CTX.session_filename_fullpath, 1, 1);
   ParseFile(CTX.options_filename_fullpath, 1, 1);

Fltk/Main.cpp

-// $Id: Main.cpp,v 1.83 2005-08-24 20:28:43 remacle Exp $
+// $Id: Main.cpp,v 1.84 2005-10-24 15:38:13 geuzaine Exp $
 //
 // Copyright (C) 1997-2005 C. Geuzaine, J.-F. Remacle
 //
@@ -71,6 +71,10 @@ int main(int argc, char *argv[])
     strcat(cmdline, " ");
   }
 
+  // Initialize the symbol tree that will hold variable names
+  
+  InitSymbols();
+
   // Initialize the static Mesh
   
   Init_Mesh0(&M);

Parser/OpenFile.cpp

-// $Id: OpenFile.cpp,v 1.84 2005-10-15 19:06:09 geuzaine Exp $
+// $Id: OpenFile.cpp,v 1.85 2005-10-24 15:38:14 geuzaine Exp $
 //
 // Copyright (C) 1997-2005 C. Geuzaine, J.-F. Remacle
 //
@@ -342,7 +342,6 @@ void OpenProblem(char *name)
   }
   CTX.threads_lock = 1;
 
-  InitSymbols();
   Init_Mesh(&M);
 
   // Initialize pseudo random mesh generator to the same seed