The 'new' system.

The X509_EXTENSION_METHOD includes extensions and attributes and/or names. 
Basically everthing that can be added to an X509 with an OID identifying it.

It operates via 2 methods per object id.
int a2i_XXX(X509 *x,char *str,int len);
int i2a_XXX(BIO *bp,X509 *x);

The a2i_XXX function will add the object with a value converted from the
string into the X509.  Len can be -1 in which case the length is calculated
via strlen(str).   Applications can always use direct knowledge to load and
unload the relevent objects themselves.

i2a_XXX will print to the passed BIO, a text representation of the
relevet object.  Use a memory BIO if you want it printed to a buffer :-).

X509_add_by_NID(X509 *x,int nid,char *str,int len);
X509_add_by_OBJ(X509 *x,ASN1_OBJECT *obj,char *str,int len);

X509_print_by_name(BIO *bp,X509 *x);
X509_print_by_NID(BIO *bp,X509 *x);
X509_print_by_OBJ(BIO *bp,X509 *x);