[GTK] Show url of history items in a status bar in MiniBrowser

[GTK] Show url of history items in a status bar in MiniBrowser
https://bugs.webkit.org/show_bug.cgi?id=71474

Reviewed by Martin Robinson.

* MiniBrowser/gtk/BrowserWindow.c:
(browserWindowSetStatusText): Set status text and show/hide the
status label.
(resetStatusText): Reset status text when history menu is hidden.
(browserWindowHistoryItemSelected): Show url of currently selected
history item.
(browserWindowCreateBackForwardMenu): Connect to hide signal of
menu to reset the status text.
(browserWindowConstructed): Use GtkOverlay if available to show
status text.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@99207 268f45cc-cd09-0410-ab3c-d52691b4dbfc