FEATURE: add vhost to the web logfile

As discussed in IRC, could we please include vhost in the webv4 logfile.

This will be useful when using the ONE_HTTP_LOG option so that we can see what domain names are being used to call the webv4 service.

Seeing this information is key to counteracting domain fronting issues.

[03:30:19 04-02-26] <DigitalMan> here are the actual values/fields of each line that file:
[03:30:20 04-02-26] <DigitalMan> 			fprintf(logfile, "%s %s %s [%s] \"%s\" %d %s \"%s\" \"%s\"\n"
[03:30:20 04-02-26] <DigitalMan> 			        , ld->hostname?(ld->hostname[0]?ld->hostname:"-"):"-"
[03:30:20 04-02-26] <DigitalMan> 			        , ld->ident?(ld->ident[0]?ld->ident:"-"):"-"
[03:30:22 04-02-26] <DigitalMan> 			        , ld->user?(ld->user[0]?ld->user:"-"):"-"
[03:30:24 04-02-26] <DigitalMan> 			        , timestr
[03:30:26 04-02-26] <DigitalMan> 			        , ld->request?(ld->request[0]?ld->request:"-"):"-"
[03:30:28 04-02-26] <DigitalMan> 			        , ld->status
[03:30:30 04-02-26] <DigitalMan> 			        , ld->size?sizestr:"-"
[03:30:33 04-02-26] <DigitalMan> 			        , ld->referrer?(ld->referrer[0]?ld->referrer:"-"):"-"
[03:30:35 04-02-26] <DigitalMan> 			        , ld->agent?(ld->agent[0]?ld->agent:"-"):"-");
[03:30:37 04-02-26] <DigitalMan> vhost isn't one of them