Feature: allow to do a hostile takeover of an AI company (in singleplayer) (#10914)

With the removal of the share-system, you could no longer make an
AI disappear in a single player game. At least, not without going
into the console.

src/widgets/company_widget.h

@@ -44,6 +44,9 @@ enum CompanyWidgets {
 	WID_C_SELECT_GIVE_MONEY,          ///< Selection widget for the give money button.
 	WID_C_GIVE_MONEY,                 ///< Button to give money.
 
+	WID_C_SELECT_HOSTILE_TAKEOVER,    ///< Selection widget for the hostile takeover button.
+	WID_C_HOSTILE_TAKEOVER,           ///< Button to hostile takeover another company.
+
 	WID_C_HAS_PASSWORD,               ///< Has company password lock.
 	WID_C_SELECT_MULTIPLAYER,         ///< Multiplayer selection panel.
 	WID_C_COMPANY_PASSWORD,           ///< Button to set company password.