Bringing in internal::shared_ptr into google:protobuf namespace.

Fixes #1029

python/google/protobuf/pyext/extension_dict.h

@@ -49,6 +49,8 @@ class FieldDescriptor;
 
 #ifdef _SHARED_PTR_H
 using std::shared_ptr;
+#else
+using internal::shared_ptr;
 #endif
 
 namespace python {

python/google/protobuf/pyext/message.h

@@ -55,6 +55,8 @@ class MessageFactory;
 #ifdef _SHARED_PTR_H
 using std::shared_ptr;
 using std::string;
+#else
+using internal::shared_ptr;
 #endif
 
 namespace python {

python/google/protobuf/pyext/message_map_container.h

@@ -47,6 +47,8 @@ class Message;
 
 #ifdef _SHARED_PTR_H
 using std::shared_ptr;
+#else
+using internal::shared_ptr;
 #endif
 
 namespace python {

python/google/protobuf/pyext/repeated_composite_container.h

@@ -51,6 +51,8 @@ class Message;
 
 #ifdef _SHARED_PTR_H
 using std::shared_ptr;
+#else
+using internal::shared_ptr;
 #endif
 
 namespace python {

python/google/protobuf/pyext/repeated_scalar_container.h

@@ -50,6 +50,8 @@ class Message;
 
 #ifdef _SHARED_PTR_H
 using std::shared_ptr;
+#else
+using internal::shared_ptr;
 #endif
 
 namespace python {

python/google/protobuf/pyext/scalar_map_container.h

@@ -47,6 +47,8 @@ class Message;
 
 #ifdef _SHARED_PTR_H
 using std::shared_ptr;
+#else
+using internal::shared_ptr;
 #endif
 
 namespace python {