minor tweaks to date handling; clear caches when config updated; ensure date formats have correct symbols

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@1234 f203690c-595d-4dc9-a70b-905162fa7fd2

src/main/java/com/healthmarketscience/jackcess/impl/ColumnImpl.java

       return ((value instanceof Double) ? value :
               toNumber(value, db).doubleValue());
     case SHORT_DATE_TIME:
-      return ((value instanceof DateExt) ? value :
+      return ((value instanceof Date) ? value :
               new Date(toDateLong(value)));
     case TEXT:
     case MEMO:

src/main/java/com/healthmarketscience/jackcess/impl/DBEvalContext.java

   private final RandomContext _rndCtx = new RandomContext();
   private Bindings _bindings = new SimpleBindings();
 
-  public DBEvalContext(DatabaseImpl db)
-  {
+  public DBEvalContext(DatabaseImpl db) {
     _db = db;
   }
 
   }
 
   public void setTemporalConfig(TemporalConfig temporal) {
-    _temporal = temporal;
+    if(_temporal != temporal) {
+      _temporal = temporal;
+      _sdfs = null;
+    }
   }
 
   public Calendar getCalendar() {
   }
 
   public void setNumericConfig(NumericConfig numeric) {
-    _numeric = numeric;
+    if(_numeric != numeric) {
+      _numeric = numeric;
+      _dfs = null;
+    }
   }
 
   public FunctionLookup getFunctionLookup() {
     SimpleDateFormat sdf = _sdfs.get(formatStr);
     if(sdf == null) {
       sdf = _db.createDateFormat(formatStr);
+      sdf.setDateFormatSymbols(_temporal.getDateFormatSymbols());
       _sdfs.put(formatStr, sdf);
     }
     return sdf;