use iswspace()/iswpunct() to find word delimiters

this inverts the configuration logic: you no longer provide a list of
delimiters -- all space and punctuation characters are considered
delimiters, unless listed in extrawordchars.

config.def.h

@@ -28,11 +28,12 @@ static float cwscale = 1.0;
 static float chscale = 1.0;
 
 /*
- * word delimiter string
+ * all space and punctuation characters are considered word delimiters, unless
+ * listed here.
  *
- * More advanced example: L" `'\"()[]{}"
+ * More advanced example: L"#$%&+,-./:=?_~"
  */
-wchar_t *worddelimiters = L" ";
+wchar_t *extrawordchars = L"./:";
 
 /* selection timeouts (in milliseconds) */
 static unsigned int doubleclicktimeout = 300;