Issue #1392208 follow-up by Gábor Hojtsy, steinmb, Artusamak, penyaskito: Re-fixed Impossible to install Drupal in a non-English language when following the provided instructions. ;)

core/INSTALL.txt

@@ -89,11 +89,14 @@ INSTALLATION
    - Download a translation file for the correct Drupal version and language
      from the translation server: http://localize.drupal.org/translate/downloads
 
-   - Place the file into your installation profile's translations
+   - Place the file into the dedicated translations directory. By default this
-     directory. For instance, if you are using the Standard install profile,
+     directory is:
-     move the .po file into the directory:
 
-       profiles/standard/translations/
+       sites/default/files/translations/
+
+     If the directory doesn't exist, you should create it. Make sure your file
+     is named drupal-VERSION.LANGCODE.po (for example, the German
+     translation for Drupal 8.0 should be named drupal-8.0.de.po).
 
    For detailed instructions, visit http://drupal.org/localize
 

core/includes/install.core.inc

@@ -1336,7 +1336,6 @@ function install_select_language_form($form, &$form_state, $files) {
     '#options' => $select_options,
     // Use the browser detected language as default or English if nothing found.
     '#default_value' => !empty($browser_langcode) ? $browser_langcode : 'en',
-    '#size' => min(count($select_options), 10),
   );
 
   if (count($files) == 1) {

core/profiles/minimal/translations/README.txt

@@ -1,3 +0,0 @@
-
-This directory should be used to place downloaded translations
-for installing Drupal core.

core/profiles/standard/translations/README.txt

@@ -1,3 +0,0 @@
-
-This directory should be used to place downloaded translations
-for installing Drupal core.