Add __hash__ delegation back

In commit 0ece970, useless
redefintions of the __hash__ methods were removed, as they
were flagged as such by pylint.

In fact, all these classes defined the __eq__ method.
In that case, the __hash__ methods would have returned None.

As external tools (like pyplusplus) rely on the fact that the __hash__
methods return something sensible for all types and declaration objects,
we need to defined these methods.

The test_hash test class has been added to make sure that
the __hash__ methods are properly implemented, as this is
part of the public API of pygccxml.

The type_qualifiers_t class will get it's __hash__ method implemented
in a separate commit, as it needs a separate test.

Author: iMichka

pygccxml/declarations/calldef_members.py

@@ -62,6 +62,8 @@ def __eq__(self, other):
             and self.has_static == other.has_static \
             and self.has_const == other.has_const
 
+    __hash__ = calldef.calldef_t.__hash__
+
     @property
     def virtuality(self):
         """Describes the "virtuality" of the member (as defined by the

pygccxml/declarations/enumeration.py

@@ -51,6 +51,8 @@ def __eq__(self, other):
             return False
         return self.values == other.values
 
+    __hash__ = declaration.declaration_t.__hash__
+
     def _get__cmp__items(self):
         """implementation details"""
         return [self.values]

pygccxml/declarations/scopedef.py

@@ -187,6 +187,8 @@ def __eq__(self, other):
             return False
         return self.declarations[:].sort() == other.declarations[:].sort()
 
+    __hash__ = declaration.declaration_t.__hash__
+
     def _get_declarations_impl(self):
         raise NotImplementedError()
 

pygccxml/declarations/typedef.py

@@ -33,6 +33,8 @@ def __eq__(self, other):
             return False
         return self.decl_type == other.decl_type
 
+    __hash__ = declaration.declaration_t.__hash__
+
     @property
     def decl_type(self):
         """reference to the original :class:`decl_type <type_t>`"""

pygccxml/declarations/variable.py

@@ -45,6 +45,8 @@ def __eq__(self, other):
             and self.value == other.value \
             and self.bits == other.bits
 
+    __hash__ = declaration.declaration_t.__hash__
+
     @property
     def decl_type(self):
         """reference to the variable :class:`decl_type <type_t>`"""