FreeBSD compatibility patches

[yurivict]

Please apply the patches * https://bitbucket.org/petsc/petsc4py/commits/ab877906425e681cbf1c64349650e54db747a727 * https://bitbucket.org/petsc/petsc4py/commits/ecf673e8b8da0d07526851716023d7ae48fe6e66

They solve the same problem that they solved in petsc4py, and the code is the same.

[Lisandro Dalcin]

I think this is already in, look at 91a49cc.