libpq++ current sources don't compile with older C++ compilers

Today I did something I usually do about once per release cycle: try to
build the system with HP's vendor cc, rather than gcc which I prefer.
This usually turns up some portability issues, and indeed I found some.
One that I'm not entirely sure about how to fix is that libpq++ no
longer builds at all:

aCC +z -I../../../src/interfaces/libpq -I../../../src/include -I/usr/local/include -c -o pgconnection.o pgconnection.cc
Error 56: "pgconnection.cc", line 20 # Namespaces are not yet implemented.
using namespace std;
^^^^^^^^^^^^^^^^^^^^

Given that we have a HAVE_NAMESPACE_STD configure symbol, I do not
understand why unconditional "using"s have been inserted into the
libpq++ files. Shouldn't these be protected by #ifdef
HAVE_NAMESPACE_STD? Or is there a different fix that's more
appropriate?

regards, tom lane