PHP 5.2 compatiblity

Namespaces are not needed so far.

https://github.com/FreshRSS/FreshRSS/commit/aacd1ffd4052b04c724c2783b3ee2845ca4ada35#commitcomment-11503581

app/Exceptions/ContextException.php

@@ -3,6 +3,6 @@
 /**
  * An exception raised when a context is invalid
  */
-class FreshRSS_Context_Exception extends \Exception {
+class FreshRSS_Context_Exception extends Exception {
 
 }

app/Exceptions/DAOException.php

@@ -1,5 +1,5 @@
 <?php
 
-class FreshRSS_DAO_Exception extends \Exception {
+class FreshRSS_DAO_Exception extends Exception {
 
 }

app/Exceptions/EntriesGetterException.php

@@ -1,5 +1,5 @@
 <?php
 
-class FreshRSS_EntriesGetter_Exception extends \Exception {
+class FreshRSS_EntriesGetter_Exception extends Exception {
 
 }

app/Exceptions/FeedException.php

@@ -1,5 +1,5 @@
 <?php
 
-class FreshRSS_Feed_Exception extends \Exception {
+class FreshRSS_Feed_Exception extends Exception {
 
 }