learn authproxy configuration option

Allow to use a another proxy for authentication than for IMAP.

Signed-off-by: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap.conf

@@ -437,6 +437,21 @@ remoterepository = RemoteExample
 #proxy = SOCKS5:IP:9999
 
 
+# TESTING: This option stands in the [Account Test] section.
+#
+# Use authproxy connection for this account. Useful to bypass the GFW in China.
+# Set this if you wish to use a proxy for authentication but not for IMAP.
+# If not explicitly set, this option defaults to use the proxy socket
+# (so as to be compatible with prior config files).
+# If that is specifically NOT desired, use authproxy = ''
+#
+# To specify a proxy connection, join proxy type, host and port with colons.
+# Available proxy types are SOCKS5, SOCKS4, HTTP.
+# You also need to install PySocks through pip or your distro package manager.
+#
+#authproxy = SOCKS5:IP:9999
+
+
 [Repository LocalExample]
 
 # Each repository requires a "type" declaration. The types supported for