proxychains.conf: fix localnet documentation

localnet with hostnames/DNS is not compatible with remote dns - if remote dns
is activated we get an ip from the remote dns resolver in the connect() call,
so we don't know whether the destination would match any localnet - except
from the ANY localnet 0.0.0.0 - in which case we would need to do a real DNS
lookup with the remote DNS ip involving both the rdns resolver to get the
original hostname back and then call the native DNS resolver function - for
which there is only getaddrinfo() when we don't want to support the 5
different gethostbyname_r() variants in existence, or using getaddrinfo(),
which in turn requires memory allocation/free() - in other words a huge mess.
we also can't easily check in the resolver whether an ANY-destination localnet
is enabled and the port matches, because the resolver might only resolve the
hostname at this stage, but not the destination port.

addressing #358

src/proxychains.conf

@@ -94,6 +94,9 @@ tcp_connect_time_out 8000
 
 ### Examples for localnet exclusion
 ## localnet ranges will *not* use a proxy to connect.
+## note that localnet works only when plain IPv4 addresses are passed to the app,
+## the hostname resolves via /etc/hosts, or proxy_dns is disabled or proxy_dns_old used.
+
 ## Exclude connections to 192.168.1.0/24 with port 80
 # localnet 192.168.1.0:80/255.255.255.0