pycsdiff: eliminate a compile-time warning

In file included from /usr/include/boost/bind.hpp:30,
                 from /usr/include/boost/python/exception_translator.hpp:10,
                 from /usr/include/boost/python.hpp:28,
                 from /home/kdudka/git/csdiff/src/pycsdiff.cc:27:
/usr/include/boost/bind.hpp:36:1: note: ‘#pragma message: The practice of declaring the Bind placeholders (_1, _2, ...) in the global namespace is deprecated. Please use <boost/bind/bind.hpp> + using namespace boost::placeholders, or define BOOST_BIND_GLOBAL_PLACEHOLDERS to retain the current behavior.’
   36 | BOOST_PRAGMA_MESSAGE(
      | ^~~~~~~~~~~~~~~~~~~~

Author: kdudka

src/pycsdiff.cc

@@ -23,6 +23,14 @@
 
 #include <sstream>
 
+// eliminate the following warning:
+//   /usr/include/boost/bind.hpp:36:1: note: ‘#pragma message: The practice
+//   of declaring the Bind placeholders (_1, _2, ...) in the global namespace
+//   is deprecated. Please use <boost/bind/bind.hpp> + using namespace
+//   boost::placeholders, or define BOOST_BIND_GLOBAL_PLACEHOLDERS to retain
+//   the current behavior.’
+#define BOOST_BIND_GLOBAL_PLACEHOLDERS
+
 #include <boost/python.hpp>
 
 std::string diff_scans(