Fix regression reported in #23 (#24)

* Add test from issue 23. Refs #23.
* Fix ptr_vector regression with incomplete types. Refs #23.
* Enable CI for feature branches

include/boost/ptr_container/ptr_vector.hpp

@@ -19,6 +19,8 @@
 #include <vector>
 #include <boost/ptr_container/ptr_sequence_adapter.hpp>
 #include <boost/ptr_container/detail/ptr_container_disable_deprecated.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/mpl/if.hpp>
 
 #if defined(BOOST_PTR_CONTAINER_DISABLE_DEPRECATED)
 #pragma GCC diagnostic push
@@ -32,16 +34,27 @@ namespace boost
     < 
         class T, 
         class CloneAllocator = heap_clone_allocator,
-        class Allocator      = std::allocator<typename ptr_container_detail::void_ptr<T>::type>
+        class Allocator      = void
     >
     class ptr_vector : public 
-        ptr_sequence_adapter< T, std::vector<
-            typename ptr_container_detail::void_ptr<T>::type,Allocator>, 
-                              CloneAllocator >
+        ptr_sequence_adapter< T,
+            std::vector<
+                typename ptr_container_detail::void_ptr<T>::type,
+                typename boost::mpl::if_<boost::is_same<Allocator, void>,
+                    std::allocator<typename ptr_container_detail::void_ptr<T>::type>, Allocator>::type
+            >,
+            CloneAllocator >
     {  
-        typedef ptr_sequence_adapter< T, std::vector<
-            typename ptr_container_detail::void_ptr<T>::type,Allocator>, 
-                                      CloneAllocator > 
+        typedef
+
+            ptr_sequence_adapter< T,
+                std::vector<
+                    typename ptr_container_detail::void_ptr<T>::type,
+                    typename boost::mpl::if_<boost::is_same<Allocator, void>,
+                        std::allocator<typename ptr_container_detail::void_ptr<T>::type>, Allocator>::type
+                >,
+                CloneAllocator >
+
             base_class;
 
         typedef ptr_vector<T,CloneAllocator,Allocator> this_type;

test/Jamfile.v2

@@ -43,4 +43,5 @@ test-suite ptr_container :
     [ compile const_element_containers.cpp ]
  #   [ sc-test null_filter_iterator ]    
   
+    [ compile issue_23.cpp ]
     ;

test/issue_23.cpp

@@ -0,0 +1,18 @@
+// Use, modification and distribution is subject to the
+// Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+ 
+#include <boost/ptr_container/ptr_vector.hpp>
+
+template<class T> struct Foo
+{
+    static void test(boost::ptr_vector<Foo<T> >& /*t*/)
+    {
+    }
+};
+
+int main()
+{
+    boost::ptr_vector<Foo<double> > ptr;
+    return 0;
+}