table: fix escaping of future funtions

Issue #1015

Author: jmcnamara

xlsxwriter/worksheet.py

@@ -3403,6 +3403,9 @@ def add_table(self, first_row, first_col, last_row, last_col, options=None):
                         # Convert Excel 2010 "@" ref to 2007 "#This Row".
                         formula = formula.replace("@", "[#This Row],")
 
+                        # Escape any future functions.
+                        formula = self._prepare_formula(formula)
+
                         col_data["formula"] = formula
                         # We write the formulas below after the table data.