Add documenation for X509_chain_up_ref()

 X509 *X509_new(void);

 void X509_free(X509 *a);

 void X509_up_ref(X509 *a);

 STACK_OF(X509) *X509_chain_up_ref(STACK_OF(X509) *x);

=head1 DESCRIPTION

X509_up_ref() increments the reference count of B<a>.

X509_chain_up_ref() increases the reference count of all certificates in

chain B<x> and returns a copy of the stack.

=head1 NOTES

The function X509_up_ref() if useful if a certificate structure is being

used by several different operations each of which will free it up after

use: this avoids the need to duplicate the entire certificate structure.

The function X509_chain_up_ref() doesn't just up the reference count of

each certificate it also returns a copy of the stack, using sk_X509_dup(),

but it serves a similar purpose: the returned chain persists after the

original has been freed.

=head1 RETURN VALUES

If the allocation fails, X509_new() returns B<NULL> and sets an error

X509_free() and X509_up_ref() do not return a value.

X509_chain_up_ref() returns a copy of the stack or B<NULL> if an error

occurred.

=head1 SEE ALSO

L<d2i_X509(3)>,