CONFIGURE: Added detection for SDL_net

configure

@@ -117,6 +117,7 @@ done
 #
 # Default lib behavior yes/no/auto
 _vorbis=auto
+_sdlnet=auto
 _tremor=auto
 _tremolo=no
 _flac=auto
@@ -3676,6 +3677,24 @@ int main(void) { return 0; }
 EOF
 cc_check -lm && append_var LIBS "-lm"
 
+#
+# Check for SDL_Net
+#
+echocheck "SDL_Net"
+if test "$_sdlnet" = auto ; then
+	_sdlnet=no
+	cat > $TMPC << EOF
+#include "SDL/SDL_net.h"
+int main(int argc, char *argv[]) { SDLNet_Init(); return 0; }
+EOF
+	cc_check $LIBS $INCLUDES -lSDL_net && _sdlnet=yes
+fi
+if test "$_sdlnet" = yes ; then
+	LIBS="$LIBS -lSDL_net"
+fi
+define_in_config_if_yes "$_sdlnet" 'USE_SDL_NET'
+echo "$_sdlnet"
+
 #
 # Check for Ogg Vorbis
 #