Since you recompiled the IRCd with added features, there is no way to rehash without a restart. I am sure your users will be forgiving if you send a global notice saying the server will restart in X amount of minutes.
In the future: Have Unreal installed to a separate location by specifying something like /home/user/UnrealIRCd/ in ./Config when it asks you for the install path. This way, you run "make install" and run it from there. When you recompile Unreal, you don't run "make install" until you are ready to restart Unreal.