bugfix: FK must have the correct column names and types.
bugfix: FK must have the correct column names and types.

If these are not satisfied, MySQL returns Error 1005 and refers to Error
150 in the error message, which means that a foreign key constraint was
not correctly formed.

danstaines/ensembl-compara,Ensembl/ensembl-compara,danstaines/ensembl-compara,Ensembl/ensembl-compara,Ensembl/ensembl-compara,danstaines/ensembl-compara,Ensembl/ensembl-compara,danstaines/ensembl-compara,Ensembl/ensembl-compara,Ensembl/ensembl-compara,danstaines/ensembl-compara,Ensembl/ensembl-compara,Ensembl/ensembl-compara