undocumenting the proxy settings [see #36]

in response to https://git.tt-rss.org/git/tt-rss/pulls/36#issuecomment-119

config.php-dist

@@ -196,9 +196,4 @@
 	// Expected config version. Please update this option in config.php
 	// if necessary (after migrating all new options from this file).
 
-	define('PROXY', '');
-	// Connect to RSS feeds through a PROXY, this way tt-rss won't connect to
-	// webservers directly.
-	// Example format: '127.0.0.1:8123' (polipo proxy running on localhost)
-
 	// vim:ft=php

include/functions.php

@@ -402,8 +402,8 @@
 				curl_setopt($ch, CURLOPT_COOKIEJAR, "/dev/null");
 			}
 
-			if (defined('PROXY')) {
+			if (defined('_HTTP_PROXY')) {
-				curl_setopt($ch, CURLOPT_PROXY, PROXY);
+				curl_setopt($ch, CURLOPT_PROXY, _HTTP_PROXY);
 			}
 
 			if ($post_query) {
@@ -495,9 +495,9 @@
                 $context_options['http']['header'] = "If-Modified-Since: $last_modified\r\n";
 			}
 
-			if (defined('PROXY')) {
+			if (defined('_HTTP_PROXY')) {
 				$context_options['http']['request_fulluri'] = true;
-				$context_options['http']['proxy'] = PROXY;
+				$context_options['http']['proxy'] = _HTTP_PROXY;
 			}
 
             $context = stream_context_create($context_options);