Add some documentation for SSL_get_shared_ciphers()

=head1 NAME

SSL_get_ciphers, SSL_get_cipher_list - get list of available SSL_CIPHERs

SSL_get_ciphers,

SSL_get_cipher_list,

SSL_get_shared_ciphers

- get list of available SSL_CIPHERs

=head1 SYNOPSIS

 STACK_OF(SSL_CIPHER) *SSL_get_ciphers(const SSL *ssl);

 const char *SSL_get_cipher_list(const SSL *ssl, int priority);

 char *SSL_get_shared_ciphers(const SSL *s, char *buf, int size);

=head1 DESCRIPTION

available, or there are less ciphers than B<priority> available, NULL

is returned.

SSL_get_shared_ciphers() creates a colon separated and NUL terminated list of

SSL_CIPHER names that are available in both the client and the server. B<buf> is

the buffer that should be populated with the list of names and B<size> is the

size of that buffer. A pointer to B<buf> is returned on success or NULL on

error. If the supplied buffer is not large enough to contain the complete list

of names then a truncated list of names will be returned. Note that just because

a ciphersuite is available (i.e. it is configured in the cipher list) and shared

by both the client and the server it does not mean that it is enabled (for

example some ciphers may not be usable by a server if there is not a suitable

certificate configured). This function will return available shared ciphersuites

whether or not they are enabled. This is a server side function only and must

only be called after the completion of the initial handshake.

=head1 NOTES

The details of the ciphers obtained by SSL_get_ciphers() can be obtained using

=item SSL_SESSION *B<SSL_get_session>(const SSL *ssl);

=item char *B<SSL_get_shared_ciphers>(const SSL *ssl, char *buf, int len);

=item char *B<SSL_get_shared_ciphers>(const SSL *ssl, char *buf, int size);

=item int B<SSL_get_shutdown>(const SSL *ssl);