Convert all header guards to pragma once

Fix some malformed if !defined() header guards

Add static to internal functions

Some objects such as PETSC_VIEWER_STDOUT_WORLD cannot be destroyed by users.

Reported-by: maitri ksh <maitri.ksh@gmail.com>

Remove git directory whose parent directory has same files

Some duplication with git commands must have happened at some point that was not noticed

Remove dead code associated to PETSC_MISSING_ERRNO_EINTR

Rename PetscValidPointer -> PetscAssertPointer

Deploy new PetscValidPointer, remove PetscValidXXXPointer

Manual linter fixes: sys

Lint apply: sys

HAVE_FORTRAN should be USE_FORTRAN_BINDINGS since it is about generating the Fortran bindings, not about if the Fortran compiler exists