Project deal.II: reset nested packages:
- Trilinos 11.10.2 seems not to be usable (seg fault) > v11.8.1
- Slepc 3.5.1: compile error petsc-arch > 3.4.4

Changes to be committed:
	modified:   deal.II/packages/petsc.package
	modified:   deal.II/packages/slepc.package
	modified:   deal.II/packages/trilinos.package