Added check for empty value of 'enable_mcserver' variable for more proper summary output.

Signed-off-by: Slava Zanko <slavazanko@gmail.com>

configure.ac

@@ -641,6 +641,10 @@ po/Makefile.in
 
 AC_OUTPUT
 
+if test x$enable_mcserver = x; then
+    enable_mcserver='no'
+fi
+
 echo "
 Configuration: