Dependecy on search module

The user, comment and node modules provide a search page, which is dependant on the search module being enabled (and the search index being created). Since search module is not required and anybody might decide to not use it (like I did :), these search features should not be displayed if the functionality is not available.

I have choosen to fix this two ways: do not display the links to the module specific search pages and do not perform any type specific search if the search module is not available.

Please apply.