[v3] Do not use __alloc_traits for forward_list::reference

[Jonathan Wakely]

        * include/bits/forward_list.h: Only include required headers.
        (forward_list::reference): Define directly, not using __alloc_traits.
        (forward_list::const_reference): Likewise.

std::forward_list is only defined in C++11 so it doesn't need to use
__alloc_traits::reference to be compatible with C++03 allocators and
can just define the reference and const_reference typedefs as
specified in C++11.

Replacing <memory> with only the required headers has a big impact on
the size of the preprocessed output of <forward_list>

Before:
$ g++ -std=c++11 -E fl.cc | wc
  25934   56245  640581
After:
$ g++ -std=c++11 -E fl.cc | wc
   8626   17685  216904

Tested x86_64-linux, committed to trunk.

commit 3755b17cf58acc001a422378602c423398c27b51
Author: Jonathan Wakely <jwakely....@gmail.com>
Date:   Sun Apr 7 16:27:18 2013 +0100

        * include/bits/forward_list.h: Only include required headers.
        (forward_list::reference): Define directly, not using __alloc_traits.
        (forward_list::const_reference): Likewise.

diff --git a/libstdc++-v3/include/bits/forward_list.h 
b/libstdc++-v3/include/bits/forward_list.h
index 608d678..8270c4e 100644
--- a/libstdc++-v3/include/bits/forward_list.h
+++ b/libstdc++-v3/include/bits/forward_list.h
@@ -32,10 +32,13 @@
 
 #pragma GCC system_header
 
-#include <memory>
-#if __cplusplus >= 201103L
 #include <initializer_list>
-#endif
+#include <bits/stl_iterator_base_types.h>
+#include <bits/stl_iterator.h>
+#include <bits/stl_algobase.h>
+#include <bits/stl_function.h>
+#include <bits/allocator.h>
+#include <ext/alloc_traits.h>
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
@@ -421,8 +424,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       typedef _Tp                                          value_type;
       typedef typename _Alloc_traits::pointer              pointer;
       typedef typename _Alloc_traits::const_pointer        const_pointer;
-      typedef typename _Alloc_traits::reference            reference;
-      typedef typename _Alloc_traits::const_reference      const_reference;
+      typedef value_type&                                 reference;
+      typedef const value_type&                                   
const_reference;
  
       typedef _Fwd_list_iterator<_Tp>                      iterator;
       typedef _Fwd_list_const_iterator<_Tp>                const_iterator;