Fix #8860: [Win32] Crashlog window wasn't reliably shown for crashes not on the main thread.

src/crashlog.h

@@ -114,6 +114,12 @@ public:
 	 */
 	static void InitialiseCrashLog();
 
+	/**
+	 * Prepare crash log handler for a newly started thread.
+	 * @note must be implemented by all implementers of CrashLog.
+	 */
+	static void InitThread();
+
 	static void SetErrorMessage(const char *message);
 	static void AfterCrashLogCleanup();
 };