vere: removes SIGQUIT handler
vere: removes SIGQUIT handler

we were turning these into SIGABRT in order to catch them and
unmap the lmdb database, but that's neither safe nor reliable.

urbit/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit