Patch by Lukas Korous: Make namespace DerivativeApproximation work with MS Visual Studio.
Keep the old data types in declarations and only use the workaround for MS Visual Studio.
Merge pull request #283 from bangerth/more-ms-vc-fixes

More ms vc fixes
DoFRenumbering::Cuthill_McKee failed in parallel when a processor had no dofs.
Add a testcase.
Merge pull request #284 from bangerth/fix-cuthill-mckee-without-dofs

Fix cuthill mckee without dofs
clarify documentation of ConstraintMatrix::distribute(VECTOR)

This came up as a question on the mailing list so we should be more precise.
Merge pull request #285 from tjhei/documentation

clarify documentation of ConstraintMatrix::distribute(VECTOR)