Fix APKs with SDK versions being reference values

This non-standard behavior is rare, but quite annoying.
The solution is simple - replacing the reference value with the actual value from integers.xml, just like Apktool already does for versionName.

brut.apktool/apktool-lib/src/main/java/brut/androlib/res/xml/ResXmlPatcher.java

@@ -197,6 +197,41 @@ public final class ResXmlPatcher {
         return null;
     }
 
+    /**
+     * Finds key in integers.xml file and returns text value
+     *
+     * @param directory Root directory of apk
+     * @param key Integer reference (ie @integer/foo)
+     * @return String|null
+     * @throws AndrolibException
+     */
+    public static String pullValueFromIntegers(File directory, String key) throws AndrolibException {
+        if (key == null || ! key.contains("@")) {
+            return null;
+        }
+
+        File file = new File(directory, "/res/values/integers.xml");
+        key = key.replace("@integer/", "");
+
+        if (file.exists()) {
+            try {
+                Document doc = loadDocument(file);
+                XPath xPath = XPathFactory.newInstance().newXPath();
+                XPathExpression expression = xPath.compile("/resources/integer[@name=" + '"' + key + "\"]/text()");
+
+                Object result = expression.evaluate(doc, XPathConstants.STRING);
+
+                if (result != null) {
+                    return (String) result;
+                }
+
+            }  catch (SAXException | ParserConfigurationException | IOException | XPathExpressionException ignored) {
+            }
+        }
+
+        return null;
+    }
+
     /**
      * Removes attributes like "versionCode" and "versionName" from file.
      *