Search form should be a template tag

[technosailor]

The search form rarely changes from theme to theme, so it would be useful for theme developers to simply have a template tag get_search() similar to get_sidebar(), get_header() and get_footer() for use in themes.

This will also serve to standardize some of the annoying nuances of themes. In this patch, the function to display the form is supplied with a filter get_searchform which would allow plugin authors to modify the searchform or theme developers to bundle a more integrated search via the themes functions.php.

[technosailor]

change to get_search_form to avoid possible collision of function names with query

[technosailor]

Updates default theme to use new tag

[technosailor]

Unified patch wrapping in all patch updates

[technosailor]

Unified patch wrapping in all patch updates

[ryan]

(In [9234]) get_search_form from technosailor. fixes #7910