If a global XQuery variable has been set in XQueryService before the compilation of the query, "declare variable ... external" may overwrite the already declared variable. Fixed.
If a global XQuery variable has been set in XQueryService before the compilation of the query, "declare variable ... external" may overwrite the already declared variable. Fixed.

svn path=/trunk/eXist-1.0/; revision=1665

ambs/exist,windauer/exist,wshager/exist,ambs/exist,wolfgangmm/exist,jensopetersen/exist,patczar/exist,shabanovd/exist,MjAbuz/exist,shabanovd/exist,RemiKoutcherawy/exist,zwobit/exist,opax/exist,zwobit/exist,patczar/exist,eXist-db/exist,jensopetersen/exist,joewiz/exist,opax/exist,windauer/exist,eXist-db/exist,wshager/exist,jessealama/exist,RemiKoutcherawy/exist,joewiz/exist,kohsah/exist,zwobit/exist,dizzzz/exist,patczar/exist,opax/exist,olvidalo/exist,adamretter/exist,wolfgangmm/exist,hungerburg/exist,RemiKoutcherawy/exist,kohsah/exist,ljo/exist,eXist-db/exist,ambs/exist,lcahlander/exist,jensopetersen/exist,ambs/exist,wshager/exist,adamretter/exist,wshager/exist,shabanovd/exist,joewiz/exist,ljo/exist,windauer/exist,jessealama/exist,MjAbuz/exist,olvidalo/exist,dizzzz/exist,olvidalo/exist,joewiz/exist,lcahlander/exist,wshager/exist,RemiKoutcherawy/exist,ljo/exist,MjAbuz/exist,lcahlander/exist,eXist-db/exist,hungerburg/exist,MjAbuz/exist,RemiKoutcherawy/exist,lcahlander/exist,eXist-db/exist,ambs/exist,opax/exist,MjAbuz/exist,opax/exist,adamretter/exist,windauer/exist,adamretter/exist,zwobit/exist,ljo/exist,dizzzz/exist,kohsah/exist,kohsah/exist,adamretter/exist,jessealama/exist,lcahlander/exist,windauer/exist,wolfgangmm/exist,shabanovd/exist,zwobit/exist,wolfgangmm/exist,ljo/exist,wshager/exist,dizzzz/exist,jensopetersen/exist,RemiKoutcherawy/exist,patczar/exist,hungerburg/exist,kohsah/exist,jensopetersen/exist,wolfgangmm/exist,lcahlander/exist,dizzzz/exist,joewiz/exist,hungerburg/exist,shabanovd/exist,jessealama/exist,ljo/exist,patczar/exist,kohsah/exist,adamretter/exist,patczar/exist,wolfgangmm/exist,jessealama/exist,eXist-db/exist,MjAbuz/exist,windauer/exist,shabanovd/exist,jensopetersen/exist,jessealama/exist,dizzzz/exist,joewiz/exist,ambs/exist,hungerburg/exist,zwobit/exist,olvidalo/exist,olvidalo/exist