Fixed install files for step-54.
Merge pull request #253 from luca-heltai/fix-step54-install-files

Fixed install files for step-54.
Fix uninitialized variables in Utilities::MPI::MinMaxAvg
Merge pull request #254 from kronbichler/fix_mpi_min_max_avg

Fix uninitialized variables in Utilities::MPI::MinMaxAvg
fixed a bug in set_matrix_mode.

STSetMatMode shall be called only after transformation_data->st
is initialised. Thus, we need to store the desired STMatMode
untill set_context is called from the solver object.
Merge pull request #246 from davydden/set_matrix_mode

fixed a bug in set_matrix_mode.
Proof read the changelog file.
Merge pull request #255 from bangerth/changelog-fixes

Proof read the changelog file.
Merge pull request #252 from kronbichler/master

Enable vectorization of vector updates in Chebyshev preconditioner
Fix undefined symbol in MPI::MinMaxAvg without MPI, commit 97bd7e2.