mpi: Add special format GCRYMPI_FMT_OPAQUE.
* src/gcrypt.h.in (GCRYMPI_FMT_OPAQUE): New. (_gcry_sexp_nth_opaque_mpi): Remove. * src/sexp.c (gcry_sexp_nth_mpi): Add support for GCRYMPI_FMT_OPAQUE. (_gcry_sexp_vextract_param): Replace removed function by GCRYMPI_FMT_OPAQUE.
Using a new formatting mode is easier than to add a dedicated
extraction function for opaque MPIs.
- Signed-off-by: Werner Koch <wk@gnupg.org>