Fix treatment of “series” option of “initval_file”

This option was treated as a numeric value: it was a hack to ensure that the
name of the dseries object was printed without quotes in the driver file.

However, that would make the JSON output synctically incorrect.

This commits removes the hack, and treats the “series” option as a string
value (in the same way as for the “data” command). A modification of the MATLAB
code will thus be needed to accomodate the change.

src/DynareBison.yy

@@ -787,7 +787,7 @@ h_options: o_filename
           | o_last_obs
           | o_data_last_obs
           | o_nobs
-          | o_series2
+          | o_series
           ;
 
 endval : ENDVAL ';' initval_list END ';'
@@ -3156,7 +3156,6 @@ o_pac_steady_state_growth : STEADY_STATE_GROWTH EQUAL signed_number { driver.set
 o_var_name : MODEL_NAME EQUAL symbol { driver.option_str("var.model_name", $3); };
 o_var_order : ORDER EQUAL INT_NUMBER { driver.option_num("var.order", $3); };
 o_series : SERIES EQUAL symbol { driver.option_str("series", $3); };
-o_series2 : SERIES EQUAL symbol { driver.option_num("series", $3); };
 o_datafile : DATAFILE EQUAL filename { driver.option_str("datafile", $3); };
 o_filename : FILENAME EQUAL filename { driver.option_str("filename", $3); };
 o_var_eq_tags : EQTAGS EQUAL vec_str { driver.option_vec_str("var.eqtags", $3); }