Add stream to buffer_group::output_unit constructor

I noticed that when creating a new output_unit, all the calls looked
like:

    m_buffered_output.emplace_back ("", indent).m_stream = stream;

It seems better to simply pass the stream to the constructor.

Approved-By: Andrew Burgess <aburgess@redhat.com>

gdb/buffered-streams.c

diff --git a/gdb/buffered-streams.c b/gdb/buffered-streams.c
index a9d3fcf..71122c7 100644
--- a/gdb/buffered-streams.c
+++ b/gdb/buffered-streams.c
@@ -51,7 +51,7 @@ buffer_group::write (const char *buf, long length_buf, ui_file *stream)
 	    && m_buffered_output.back ().m_msg.back () != '\n')
 	  m_buffered_output.back ().m_msg.append (msg);
 	else
-	  m_buffered_output.emplace_back (msg).m_stream = stream;
+	  m_buffered_output.emplace_back (stream, msg);
 	prev = cur + 1;
       }
 }
@@ -61,7 +61,7 @@ buffer_group::write (const char *buf, long length_buf, ui_file *stream)
 void
 buffer_group::wrap_here (int indent, ui_file *stream)
 {
-  m_buffered_output.emplace_back ("", indent).m_stream = stream;
+  m_buffered_output.emplace_back (stream, "", indent);
 }
 
 /* See buffered-streams.h.  */
@@ -69,7 +69,7 @@ buffer_group::wrap_here (int indent, ui_file *stream)
 void
 buffer_group::flush_here (ui_file *stream)
 {
-  m_buffered_output.emplace_back ("", -1, true).m_stream = stream;
+  m_buffered_output.emplace_back (stream, "", -1, true);
 }
 
 /* See buffered-streams.h.  */

gdb/buffered-streams.h

diff --git a/gdb/buffered-streams.h b/gdb/buffered-streams.h
index 0da2d8a..9da45b0 100644
--- a/gdb/buffered-streams.h
+++ b/gdb/buffered-streams.h
@@ -48,8 +48,10 @@ struct buffer_group
 
   struct output_unit
   {
-    output_unit (std::string msg, int wrap_hint = -1, bool flush = false)
-      : m_msg (msg), m_wrap_hint (wrap_hint), m_flush (flush)
+    output_unit (ui_file *stream, std::string msg, int wrap_hint = -1,
+		 bool flush = false)
+      : m_stream (stream), m_msg (msg), m_wrap_hint (wrap_hint),
+	m_flush (flush)
     {}
 
     /* Write contents of this output_unit to the underlying stream.  */