[zendframework/zendframework#3261] use -f switch instead of -r

- "-r" is evidently a deprecated/obsolete synonym for "-f", and not
  present on current versions of sendmail (though still present on many
  clones, including postfix, exim, and qmail)
  - updated tests to refer to "-f" instead of "-r"

src/Transport/Sendmail.php

@@ -252,7 +252,7 @@ protected function prepareParameters(Mail\Message $message)
         if (count($from)) {
             $from->rewind();
             $sender      = $from->current();
-            $parameters .= ' -r ' . $sender->getEmail();
+            $parameters .= ' -f ' . $sender->getEmail();
             return $parameters;
         }
 

test/Transport/SendmailTest.php

@@ -89,7 +89,7 @@ public function testReceivesMailArtifactsOnUnixSystems()
         $this->assertContains("From: zf-devteam@zend.com,\r\n Matthew <matthew@zend.com>\r\n", $this->additional_headers);
         $this->assertContains("X-Foo-Bar: Matthew\r\n", $this->additional_headers);
         $this->assertContains("Sender: Ralph Schindler <ralph.schindler@zend.com>\r\n", $this->additional_headers);
-        $this->assertEquals('-R hdrs -r ralph.schindler@zend.com', $this->additional_parameters);
+        $this->assertEquals('-R hdrs -f ralph.schindler@zend.com', $this->additional_parameters);
     }
 
     public function testReceivesMailArtifactsOnWindowsSystems()