Added config support for building with IPX

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@1666

configure.in

@@ -152,6 +152,16 @@ else
    AC_MSG_WARN([Can't find SDL_net, internal modem disabled])
 fi
 
+AH_TEMPLATE(C_IPX,[Define to 1 to enable IPX over Internet networking, requires SDL_net])
+AC_CHECK_HEADER(SDL/SDL_net.h,have_sdl_net_h=yes,)
+AC_CHECK_LIB(SDL_net, SDLNet_Init, have_sdl_net_lib=yes, , )
+if test x$have_sdl_net_lib = xyes -a x$have_sdl_net_h = xyes ; then
+  LIBS="$LIBS -lSDL_net"
+   AC_DEFINE(C_IPX,1)
+else 
+   AC_MSG_WARN([Can't find SDL_net, IPX networking disabled])
+fi
+
 AH_TEMPLATE(C_OPENGL,[Define to 1 to use opengl display output support])
 AC_ARG_ENABLE(opengl,AC_HELP_STRING([--disable-opengl],[Disable opengl support]),,enable_opengl=yes)
 AC_CHECK_LIB(GL, main, have_gl_lib=yes, have_gl_lib=no , )