added param in InstrospectionProcessor __construct to allow stacktrace offset

src/Monolog/Processor/IntrospectionProcessor.php

@@ -30,15 +30,18 @@ class IntrospectionProcessor
 
     private $skipClassesPartials;
 
+    private $extra_stack;
+
     private $skipFunctions = array(
         'call_user_func',
         'call_user_func_array',
     );
 
-    public function __construct($level = Logger::DEBUG, array $skipClassesPartials = array())
+    public function __construct($level = Logger::DEBUG, array $skipClassesPartials = array(), $extra_stack = 0)
     {
         $this->level = Logger::toMonologLevel($level);
         $this->skipClassesPartials = array_merge(array('Monolog\\'), $skipClassesPartials);
+        $this->extra_stack = $extra_stack;
     }
 
     /**
@@ -77,6 +80,8 @@ class IntrospectionProcessor
             break;
         }
 
+        $i += $this->extra_stack;
+
         // we should have the call source now
         $record['extra'] = array_merge(
             $record['extra'],