fix 1798 output

It seems calling ##fileinfo->getFilename()## twice outputs the empty string the second time. Document that in the test for now and look at it later.

hphp/test/slow/ext_iterator/1798.php

@@ -27,8 +27,9 @@ foreach ($iterator as $fileinfo) {
   }
 }
 ksort($files);
-foreach ($files as $fileinfo) {
-  echo "BEGIN: " . $fileinfo->getFilename() . "\n";
+foreach ($files as $name => $fileinfo) {
+  echo "BEGIN: " . $name . "\n";
+  echo $fileinfo->getFilename() . "\n";
   echo $fileinfo->getCTime() . "\n";
   echo $fileinfo->getBasename() . "\n";
   echo $fileinfo->getBasename('.cpp') . "\n";
@@ -56,7 +57,7 @@ foreach ($iterator as $fileinfo) {
   }
 }
 ksort($files);
-foreach ($files as $fileinfo) {
+foreach ($files as $name => $fileinfo) {
   echo $fileinfo->getFilename() . "\n";
   echo $fileinfo->getCTime() . "\n";
   echo $fileinfo->getBasename() . "\n";

hphp/test/slow/ext_iterator/1798.php.expectf

@@ -11,7 +11,8 @@ array(5) {
   [4]=>
   string(7) "symlink"
 }
-BEGIN:
+BEGIN: empty
+
 %d
 
 
@@ -29,7 +30,8 @@ dir
 1
 1
 END
-BEGIN:
+BEGIN: file
+
 %d
 
 
@@ -47,7 +49,8 @@ dir
 1
 1
 END
-BEGIN:
+BEGIN: fix_mtimes.inc
+
 %d
 
 
@@ -65,7 +68,8 @@ dir
 1
 1
 END
-BEGIN:
+BEGIN: symlink
+
 %d