ob-exp: Fix code indentation after src block evaluation

* lisp/ob-exp.el (org-export-blocks-preprocess): Do not use
  `indent-code-rigidly' as it doesn't indent contents of strings.
org-export: Fix smart quote bug with footnote definitions in ascii back-end

* contrib/lisp/org-export.el (org-export-activate-smart-quotes): Fix
  error when exporting a footnote definition.