Add GDB pretty-printers for zend_string, zend_type

Author: arnaud-lb

.gdb.py

@@ -32,7 +32,10 @@ def to_string(self):
 
     def children(self):
         for field in self.val.type.fields():
-            yield (field.name, self.val[field.name])
+            if field.name == 'val':
+                yield ('val', self.format_string())
+            else:
+                yield (field.name, self.val[field.name])
 
     def format_string(self):
         len = int(self.val['len'])