http proxy support by setting NETWORK_PROXY variable

This should implement feature request in #919.

defaults.lua

@@ -178,6 +178,11 @@ KOBO_LIGHT_ON_START = -1           -- -1 or 0-100. -1 leaves light as it is, oth
 KOBO_SCREEN_SAVER = ""             -- image or directory with pictures or "-"
 KOBO_SCREEN_SAVER_LAST_BOOK = true -- get screensaver from last book if possible
 
+-- Network proxy settings
+-- proxy url should be a string in the format of "http://localhost:3128"
+-- proxy authentication is not supported yet.
+NETWORK_PROXY = nil
+
 -- ####################################################################
 -- following features are not supported right now
 -- ####################################################################

frontend/ui/networkmgr.lua

@@ -83,4 +83,10 @@ function NetworkMgr:getWifiStatus()
     return false
 end
 
+-- set network proxy if global variable NETWORK_PROXY is defined
+if NETWORK_PROXY then
+    local http = require("socket.http")
+    http.PROXY = NETWORK_PROXY
+end
+
 return NetworkMgr