Accessibility test fails with the search form of Drupal

Hi all,
We are developing several spanish eGovernment web sites, and the main point we want to obtain is a good accesibility acording to W3C, we are using TAW (Web Accessibility Test) http://www.tawdis.net/. We have experienced two accesibility problems on the search form. This is the result of our TAW-analysis:

Associate labels explicitly with their controls.

• This form control is not explicitly associated with a label. (1)
• Line 40: name="search_theme_form_keys" id="edit-search-theme-form-keys" size="15"
  value="" title="Insert the words you want to search"
  class="form-text" />

First error: the search form do not contains a text item on the 'value'
of the form, this must be corrected, the solution would be adding
"Search..." on the edit box.

Second error: The form doesn't have the tag LABEL with the name of the
search form ID. The solution is adding: for="edit-search-theme-form-keys"> before the tag "... type="text"..."

So, the solution we propose is:

<div id="search" class="container-inline"><div class="form-item">
<b>CHANGE 1 (ADDING A LABEL)</b> <LABEL for="edit-search-theme-form-keys"></LABEL>
<b>CHANGE 2 (ADDING A VALUE)</b> <input type="text" maxlength="128" name="search_theme_form_keys" id="edit-search-theme-form-keys" size="15" value="Search..." title="Insert the words you want to search" class="form-text" />

Is it posible to add in the core of Drupal?
For a manual change, where is the generator file of this search form?

thanks in advance!

joan