zvt/gnome-utmp.c and WTMPX_FILE

[Dan Newcombe <Newcombe mordor clayton edu>]

I was compiling gnome-libs out of CVS (from this morning) and it dies on
zvt/gnome-utmp.c because WTMPX_FILE is not defined.

I'm not sure of the best way to fix this...the config script assumes that
if you have utmpx.h that you have WTMPX_FILE.  On HPUX this is not true
(Boy...I'm starting to hate HPUX!).  

On HPUX, to get gnome-libs to compile, you have to ignore the fact that
you have utmpx.h and let the built-in code take care of things.

(On a related note, to get most things to compile I have to define
_XOPEN_SOURCE_EXTENDED...where in the autoconf scheme of things would be a
good place to put this once and for all so I don't have to keep editing
Makefiles?)

I am assuming this could be fixed in the configure.in, but not knowing
much about how all that works, I wouldn't want to take as stab at fixing
it myself. (actually the below worked...but I'm not sure if it is 100%
correct)
AC_TRY_COMPILE(
[#include <utmpx.h>
int main() { int i=WTMPX_FILE; return 0; }],
        has_wtmpx=yes,
        has_wtmpx=no)
        AC_MSG_RESULT($has_wtmpx)
        if test "$has_wtmpx" = yes; then
                AC_DEFINE(HAVE_UTMPX_H)
        fi
AC_CHECK_HEADERS( pty.h libutil.h)