add ability to set codepage explicitly for BIFF5

If BIFF5 excel 95 file doesn't have codepage record, the default codepage CP1252 is used and can't be change.
That causes to problems with decoding cyrillic text.

Author: boltunoreh

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 
 - Support writing to streams in all writers [#1292](https://github.com/PHPOffice/PhpSpreadsheet/issues/1292)
 - Support CSV files with data wrapping a lot of lines [#1468](https://github.com/PHPOffice/PhpSpreadsheet/pull/1468)
+- Add ability to set codepage explicitly for BIFF5 [#1018](https://github.com/PHPOffice/PhpSpreadsheet/issues/1018)
 
 ### Fixed
 

src/PhpSpreadsheet/Reader/Xls.php

@@ -439,6 +439,14 @@ public function canRead($pFilename)
         }
     }
 
+    /**
+     * @param string $codepage
+     */
+    public function setCodepage($codepage): void
+    {
+        $this->codepage = $codepage;
+    }
+
     /**
      * Reads names of the worksheets from a file, without parsing the whole file to a PhpSpreadsheet object.
      *
@@ -640,7 +648,7 @@ public function load($pFilename)
 
         // initialize
         $this->pos = 0;
-        $this->codepage = 'CP1252';
+        $this->codepage = $this->codepage == null ? 'CP1252' : $this->codepage;
         $this->formats = [];
         $this->objFonts = [];
         $this->palette = [];