add option to print_var_error() function to delegate errors to error->one() instead of error->all()

this change is applied to cases that may happen on individual ranks only, e.g. out-of-range access, division by zero, invalid argument.

src/variable.h

@@ -125,7 +125,7 @@ class Variable : protected Pointers {
   double constant(char *);
   int parse_args(char *, char **);
   char *find_next_comma(char *);
-  void print_var_error(const char *, int, const char *, int);
+  void print_var_error(const char *, int, const char *, int, int global=1);
   void print_tree(Tree *, int);
 };