Skip retrieval of menu path on front page

I have found a bug that appears to be almost identical to the following fixed issue with menu_breadcrumb module:

#492572: Skip retrieval of menu path on front page

I have a multilingual site, which has French as the default language. After installing this module, I noticed that my primary links were no longer visible on the English home page. The attached patch fixes the problem for me, it ensures that menu functions don't get called in menu_breadcrumb_init() if the current page is the front page. This patch has the added benefit of ensuring that the Home link on the front page always points to the front page, which would fix issues like this #278148: menu breadcrumb leads to wrong "home" breacrumb on startpage.

Patch forthcoming.