Inline cascading stylesheets from drupal_add_css()

Attached upgrade routine changes drupal_set_html_head() calls that contain inline css to drupal_add_css().

Test function:

function example_drupal_set_html_head_css() {
  $color = variable_get('backgroundcolor', '#FFFFFF');
  drupal_set_html_head("<style type='text/css'>body {background-color: $color}</style>");
  
  drupal_set_html_head('<style type="text/css">div {background-url: url("images/test.png");}</style>');
  drupal_set_html_head('
    <style type="text/css">
      div {
        background-url: url("images/test.png");
      }
    </style>
  ');
}