Add doc blocks to functions that are missing them.

If the function has no need for `@param` or `@return`, do an archeaological dig to find `@since`.

See #32444.


git-svn-id: https://develop.svn.wordpress.org/trunk@32672 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/theme-install.php

@@ -135,6 +135,9 @@ function install_themes_dashboard() {
 <?php
 }
 
+/**
+ * @since 2.8.0
+ */
 function install_themes_upload() {
 ?>
 <p class="install-help"><?php _e('If you have a theme in a .zip format, you may install it by uploading it here.'); ?></p>