Added .odp writing back

.odp writing now works, using a workaround for the following issue:
PHPOffice/PHPPresentation#21

As of now, the presentation gets written to both a .pptx and a .odp
file.

build.php

@@ -217,12 +217,22 @@ function getTime($s, $hour=0, $minute=0, $second=0, $base=NULL) {
 }
 
 
-$odpFile = strftime($config['odp']['path'], $startDate);
-echo 'Saving Powerpoint presentation file as '.$odpFile.' ... <br />';
+$pptFile = strftime($config['ppt']['path'], $startDate);
+echo 'Saving Powerpoint presentation file as '.$pptFile.' ... <br />';
 $objWriter = PHPPowerPoint_IOFactory::createWriter($ppt, 'PowerPoint2007');
-$objWriter->save($odpFile);
+$objWriter->save($pptFile);
+
 
+// set locale to work around bugs: ODPresentation writer needs to be run
+// on a locale that uses the dot (.) as decimal mark, otherwise the documents
+// will be invalid. This has been filed as issue #21 at
+// https://github.com/PHPOffice/PHPPowerPoint/issues/21
+setlocale(LC_ALL, 'en_US.utf8');
 
+$odpFile = strftime($config['odp']['path'], $startDate);
+echo 'Saving LibreOffice Impress presentation file as '.$odpFile.' ... <br />';
+$odpWriter = PHPPowerPoint_IOFactory::createWriter($ppt, 'ODPresentation');
+$odpWriter->save($odpFile);
 
 
 echo '<hr /><a href="index.php">Zurück zum Formular</a>';