Set default size of array_t when no size is defined

This will allow to easier mock type_t classes in
the tests

Author: iMichka

pygccxml/declarations/cpptypes.py

@@ -608,8 +608,10 @@ class array_t(compound_t):
     """represents C++ array type"""
     SIZE_UNKNOWN = -1
 
-    def __init__(self, base, size):
+    def __init__(self, base, size=None):
         compound_t.__init__(self, base)
+        if size is not None:
+            size = self.SIZE_UNKNOWN
         self._size = size
 
     @property