Fix building in C++14 mode.
See also: https://bugs.gentoo.org/show_bug.cgi?id=600774

--- a/media/Ac3d.cc
+++ b/media/Ac3d.cc
@@ -892,7 +892,7 @@
 	m_rotation (rotation)
   {
 	std::ifstream is (m_file.c_str ());
-	if (is == 0)
+	if (!is)
 	  {
 		throw No_File (m_file);
 	  }
--- a/media/XML_Parser.cc
+++ b/media/XML_Parser.cc
@@ -391,7 +391,7 @@
 {
   m_file = file;
   mp_stream = new std::ifstream (file.c_str ());
-  if ((mp_stream == 0) || (*mp_stream == 0))
+  if ((mp_stream == NULL) || (!(*mp_stream)))
 	{
 	  throw No_XML_File (m_file);
 	}