fix typos in doc/news/changes.h
Merge pull request #272 from felgru/typos

fix typos in doc/news/changes.h
Merge pull request #271 from kronbichler/master

Include mpi.h in base/config.h to avoid Intel compile error
Improve grammar of error message.
Merge pull request #274 from bangerth/doc-fixes-11

Improve grammar of error message.
Improve error message for out-of-bound access in parallel vector