Merge pull request #364 from giox069/next

Rename relevant CB_FORMAT to CF, many thanks to @tachylatus.
Fix possible crash when closing RDP connection

Fixes a crash detected on remmina 1.2 when closing a connection
window with alt-f4
GTK3 migration - GTK_STOCK deprecated
GTK3 upgrade - gtk_action_is_sensitive has been deprecated since version 3.10
GTK3 upgrade - GTK_STOCK deprecated and gtk_image_set_from_stock #365
GTK3 upgrade - GTK_GRID fixes #365