Examples
ex3.c: Tests dynamic loading of viewer.
ex4.c: Tests PetscOptionsCreateViewer() via checking output of PetscViewerASCIIPrintf().
ex5.c: Tests PetscOptionsPushGetViewerOff() via checking output of PetscViewerASCIIPrintf().
ex6.c: Tests binary viewers.
ex7.c: Test PetscOptionsCreateViewers()";