add support for "proxy_dns_old" to use old 3.1 DNS lookup method

some lamer on IRC by the name of annoner/R3M0RS3/penis was complaining
that 3.1 is a lot better than proxychains-ng, because it happens to
work with the browser he's interested in.
since this wasn't the first time this is requested, let's give this
those lamers what they want: lame code!

src/proxychains.conf

@@ -49,7 +49,15 @@ strict_chain
 #quiet_mode
 
 # Proxy DNS requests - no leak for DNS data
-proxy_dns 
+# this uses the proxychains4 style method to do remote dns
+proxy_dns
+
+# use the old proxyresolv script to proxy DNS requests
+# in proxychains 3.1 style. requires proxyresolv in $PATH
+# plus a dynamically linked `dig` binary.
+# this is a lot slower than `proxy_dns`, doesn't support .onion URLs,
+# but might be more compatible with complex software like webbrowsers.
+#proxy_dns_old
 
 # set the class A subnet number to use for the internal remote DNS mapping
 # we use the reserved 224.x.x.x range by default,