MDL-41115 fix username field label when allowing login via email

Thanks Marina for spotting this!

lang/en/moodle.php

@@ -1897,6 +1897,7 @@ $string['userdetails'] = 'User details';
 $string['userfiles'] = 'User files';
 $string['userlist'] = 'User list';
 $string['username'] = 'Username';
+$string['usernameemail'] = 'Username / email';
 $string['usernameemailmatch'] = 'The username and email address do not relate to the same user';
 $string['usernameexists'] = 'This username already exists, choose another';
 $string['usernamelowercase'] = 'Only lowercase letters allowed';

login/index_form.html

@@ -10,6 +10,11 @@ if (!empty($CFG->loginpasswordautocomplete)) {
 } else {
     $autocomplete = '';
 }
+if (empty($CFG->authloginviaemail)) {
+    $strusername = get_string('username');
+} else {
+    $strusername = get_string('usernameemail');
+}
 ?>
 <div class="loginbox clearfix <?php echo $columns ?>">
   <div class="loginpanel">
@@ -30,7 +35,7 @@ if (!empty($CFG->loginpasswordautocomplete)) {
         ?>
         <form action="<?php echo $CFG->httpswwwroot; ?>/login/index.php" method="post" id="login" <?php echo $autocomplete; ?> >
           <div class="loginform">
-            <div class="form-label"><label for="username"><?php print_string("username") ?></label></div>
+            <div class="form-label"><label for="username"><?php echo($strusername) ?></label></div>
             <div class="form-input">
               <input type="text" name="username" id="username" size="15" value="<?php p($frm->username) ?>" />
             </div>