Uncommon logger levels in Friendica (#5453)

* "normal" is an uncommon logger level:
- changed LOGGER_NORMAL -> LOGGER_INFO
- added LOGGER_WARNING (a common logger level)

* Used constants instead of values (MrPetovan)

src/Util/Network.php

@@ -220,7 +220,7 @@ class Network
 		}
 
 		if (curl_errno($ch) !== CURLE_OK) {
-			logger('error fetching ' . $url . ': ' . curl_error($ch), LOGGER_NORMAL);
+			logger('error fetching ' . $url . ': ' . curl_error($ch), LOGGER_INFO);
 		}
 
 		$ret['errno'] = curl_errno($ch);