Fix for Bug 6970 - logout not redirecting to login page

Fix for Bug 6970 - logout not redirecting to login page

For some reason the latest version of Firefox doesn't like
the javascript which empties the cart on logout. As Ian points
out, there is code which tries to redirect to "about:blank"
and close the window (since the main context of the function
is the Cart's popup window.

This patch adds a parameter to the delBasket function so
that we can pass a "popup" context to the function and
choose whether or not we want to ask JS to close the window.

Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>