environment override variables are printed to stderr

[slingamn]

Reported by eta in #ergo. This almost seems like a debugging print that got left in the release:

ergo/irc/config.go

Lines 1129 to 1131 in c67835c

	} else if applied {
	log.Printf("applied environment override: %s\n", envPair)
	}

We can't log at level debug because we don't have the actual logger yet. Let's print the variable name but not the value.

[slingamn]

Incidentally, an envvar override with an invalid format will panic

ergo/irc/config.go

Lines 1047 to 1048 in c67835c

	equalIdx := strings.IndexByte(envPair, '=')
	name, value := envPair[:equalIdx], envPair[equalIdx+1:]

(never mind, I forgot how os.Environ works)