OpenSSL generate_host_certificate(): Use config.privoxy.org as Common Name

OpenSSL generate_host_certificate(): Use config.privoxy.org as Common Name

... Org and Org Unit if the real host name is too long to
get accepted by OpenSSL.

Prevents failures like:
2021-03-15 10:04:34.318 802816f00 Error: X509 subject name (code: CN, val: only-d-pmjr9f4mclevwwl2mwckreicm8k1afzk-1615774207025.nstool.netease.com) error: error:0D07A097:asn1 encoding routines:ASN1_mbstring_ncopy:string too

Clients should only care about the Subject Alternative Name
anyway and we can continue to use the real host name for it.

Reported by Miles Wen on privoxy-users@.