Bug 1095436: Export MOZ_B2G_BT_DAEMON in configure.in, r=mh+mozilla

This change is required to use bluetoothd in Gecko. It probably
got lost while rebasing the patches of bug 1073548.

configure.in

@@ -7560,6 +7560,7 @@ fi
 AC_SUBST(MOZ_B2G_BT)
 AC_SUBST(MOZ_B2G_BT_BLUEZ)
 AC_SUBST(MOZ_B2G_BT_BLUEDROID)
+AC_SUBST(MOZ_B2G_BT_DAEMON)
 
 dnl ========================================================
 dnl = Enable NFC Interface for B2G (Gonk usually)