more fixes after the repository split:
more fixes after the repository split:

SQL_BACKEND is no longer set by configure[.ag];
but since the statically linked Mserver (currently?) only relevant
for/with the MonetDB4 backend, we can simply hard-wire "monet4".

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb