sexp: Support reading base64.
* configure.ac (NEED_GPG_ERROR_VERSION): Require libgpg-error >= 1.27. * src/sexp.c (do_vsexp_sscan): Support data in base64 format. * tests/t-sexp.c (check_extract_param): Add a test case.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>