Rewrite mft.c and roa.c with ASN.1 templates

Rewrite mft.c and roa.c with ASN.1 templates

The ASN.1 templates are a rather direct translation of the ASN.1 in the
relevant RFCs and they allow deserializing the Manifest and ROA eContent
in a single step instead of numerous opaque d2i_ASN1_SEQUENCE_ANY() calls.
Once the eContent is deserialized, we can walk the structs, validate it
as before and populate the internal data structures.

Positive feedback job
ok claudio