The link under the pointer, for the host to show where it leads
A browser shows at the bottom of the window where the link under the mouse leads, but ltk-webkit did not tell its host which link that was. `WebView::hovered_link` gives the address of the link the pointer is over, as of its last motion over the page, or `None` over anything else.
On WPE the new `hover.rs` connects WebKit's `mouse-target-changed`, whose hit test gives the link's address, and keeps it in `Inner::hovered_link`. `context_menu::text`, which copies a hit test's string, is shared with it. On CEF it is the display handler's `on_status_message`, which is what Chromium shows in its status bubble, an empty message clearing it. The table of what reaches the host in `lib.rs` lists it.
Not done. WebKit tells only on a motion, so after a load the previous page's link stays until the pointer moves, and the host has to tell that case apart.
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# Cambios a ser confirmados:
#	modificados:     src/cef/display.rs
#	modificados:     src/cef/mod.rs
#	modificados:     src/lib.rs
#	modificados:     src/wpe/context_menu.rs
#	nuevos archivos: src/wpe/hover.rs
#	modificados:     src/wpe/mod.rs
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