Add workaround to be able to use SLEPc >= 3.5.0 with deal.II. This requires disabling support for STFOLD spectrum transformation type since it was removed in SLEPc 3.5.0 and newer.

Also log the corresponding entry in changes.h
Merge pull request #87 from agrayver/latest_slepc_support

Add workaround to be able to use SLEPc >= 3.5.0 with deal.II.