moc fails to parse BOOST_JOIN macro of boost library

boost provides BOOST_JOIN macro:

//
// Helper macro BOOST_JOIN:
// The following piece of macro magic joins the two
// arguments together, even when one of the arguments is
// itself a macro (see 16.3.1 in C++ standard). The key
// is that macro expansion of macro arguments does not
// occur in BOOST_DO_JOIN2 but does in BOOST_DO_JOIN.
//
#define BOOST_JOIN( X, Y ) BOOST_DO_JOIN( X, Y )
#define BOOST_DO_JOIN( X, Y ) BOOST_DO_JOIN2(X,Y)
#define BOOST_DO_JOIN2( X, Y ) X##Y

This macro is not new in dev-libs/boost:1.48, but it is now used in more
places.
Some packages (e.g. sci-chemistry/avogadro) use moc and headers of
dev-libs/boost.

The attached test header shows parse error. (A separate bug is that moc
truncates name of header in error message.)

$ moc -I/usr/include test.h -o test.moc
usr/include/boost-1_48/boost/type_traits/detail/has_binary_operator.hp:50:
Parse error at "BOOST_JOIN"

Line 50 in
/usr/include/boost-1_48/boost/type_traits/detail/has_binary_operator.hpp is:

namespace BOOST_JOIN(BOOST_TT_TRAIT_NAME,_impl) {

Initial bug report on GentoO Bugzilla: https://bugs.gentoo.org/show_bug.cgi?id=401551