pki_gcrypt: Rework 'pki_publickey_to_blob'
pki_gcrypt: Rework 'pki_publickey_to_blob'

* src/pki_gcrypt.c (pki_publickey_to_blob): Rework using the new
helper 'ssh_sexp_extract_mpi'.

Signed-off-by: Justus Winter <4d1bd7a5ca1cd26bee0df05b6801a6ce9a22196e@g10code.com>
Reviewed-by: Andreas Schneider <5be00ddc76278cf6077f5047ca3384a88460c671@cryptomilk.org>

kedazo/libssh,kedazo/libssh,kedazo/libssh,kedazo/libssh