[libxml++] Fix the build with C++11 compilers, such as MS Visual C++ 2013.

[Murray Cumming <murrayc src gnome org>]

commit 7dbfb0aed508451e8237c34472815e44925a545c
Author: Mikhail Titov <mlt gmx us>
Date:   Thu Apr 30 17:51:20 2015 +0200

    Fix the build with C++11 compilers, such as MS Visual C++ 2013.
    
    Implicit conversions from streams to bool are no longer allowed.

 libxml++/io/istreamparserinputbuffer.cc |    2 +-
 libxml++/io/ostreamoutputbuffer.cc      |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/libxml++/io/istreamparserinputbuffer.cc b/libxml++/io/istreamparserinputbuffer.cc
index b1d6e5b..7a7f283 100644
--- a/libxml++/io/istreamparserinputbuffer.cc
+++ b/libxml++/io/istreamparserinputbuffer.cc
@@ -39,6 +39,6 @@ namespace xmlpp
 
   bool IStreamParserInputBuffer::do_close()
   {
-    return input_;
+    return input_.good();
   }
 }
diff --git a/libxml++/io/ostreamoutputbuffer.cc b/libxml++/io/ostreamoutputbuffer.cc
index 0a3e6db..b23a8b6 100644
--- a/libxml++/io/ostreamoutputbuffer.cc
+++ b/libxml++/io/ostreamoutputbuffer.cc
@@ -29,13 +29,13 @@ namespace xmlpp
     // here we rely on the ostream implicit conversion to boolean, to know if the stream can be used and/or 
if the write succeded.
     if(output_)
       output_.write(buffer, len);
-    return output_;
+    return output_.good();
   }
 
   bool OStreamOutputBuffer::do_close()
   {
     if(output_)
         output_.flush();
-    return output_;
+    return output_.good();
   }
 }