Document RFC5114 "generation" options.

The value to use for the generator B<g>.

=item B<dh_rfc5114:num>

If this option is set then the appropriate RFC5114 parameters are used

instead of generating new parameters. The value B<num> can take the

values 1, 2 or 3 corresponding to RFC5114 DH parameters consisting of

1024 bit group with 160 bit subgroup, 2048 bit group with 224 bit subgroup

and 2048 bit group with 256 bit subgroup as mentioned in RFC5114 sections

2.1, 2.2 and 2.3 respectively.

=back

=head1 EC PARAMETER GENERATION OPTIONS

 openssl genpkey -genparam -algorithm DH -out dhp.pem \

					-pkeyopt dh_paramgen_prime_len:1024

Output RFC5114 2048 bit DH parameters with 224 bit subgroup:

 openssl genpkey -genparam -algorithm DH -out dhp.pem -pkeyopt dh_rfc5114:2

Generate DH key from parameters:

 openssl genpkey -paramfile dhp.pem -out dhkey.pem