DOC: typos / small errors in comments / docstrings

Cleanup of nifti1 with spellchecker
RF: remove Freesurfer hack for shape in Nifti2

Freesurfer hack is for long vectors.  No need for this with Nifti2
because of the int64 dimensions.
BF: fix incorrect EOL check in header

I misread the spec, and used decimal 32 when it should have been octal.