Find the start and end point of an element in a DER encoding
string. I mean that if you have a der encoding and you have already
used the function asn1_der_decoding() to fill a structure, it may
happen that you want to find the piece of string concerning an
element of the structure.
One example is the sequence "tbsCertificate" inside an X509
ASN1_SUCCESS if DER encoding OK, ASN1_ELEMENT_NOT_FOUND
if ELEMENT is ASN1_TYPE EMPTY or name_element is not a valid
element, ASN1_TAG_ERROR or ASN1_DER_ERROR if the der encoding
doesnt match the structure ELEMENT.