[PATCH] Reduce header dependencies in <iterator>

[Jonathan Wakely]

	* include/std/iterator: Include <iosfwd> instead of <istream> and
	<ostream>.

This makes <iterator> 5kloc smaller!

Tested powerpc64le-linux, committed to trunk.

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commit 32a8a4b2518030b683561d26ef64c301b46deb5a
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Feb 23 20:13:37 2017 +0000

    Reduce header dependencies in <iterator>
    
            * include/std/iterator: Include <iosfwd> instead of <istream> and
            <ostream>.

diff --git a/libstdc++-v3/include/std/iterator b/libstdc++-v3/include/std/iterator
index 9d9e19c4c6b..28e7c65a9e5 100644
--- a/libstdc++-v3/include/std/iterator
+++ b/libstdc++-v3/include/std/iterator
@@ -61,8 +61,7 @@
 #include <bits/stl_iterator_base_types.h>
 #include <bits/stl_iterator_base_funcs.h>
 #include <bits/stl_iterator.h>
-#include <ostream>
-#include <istream>
+#include <iosfwd>
 #include <bits/stream_iterator.h>
 #include <bits/streambuf_iterator.h>
 #include <bits/range_access.h>