sapi: New implementation of rtems_panic()

The previous rtems_panic() implementation was quite heavy weight.  It
depended on _exit() which calls the global destructors.  It used
fprintf(stderr, ...) for output which depends on an initialized console
device and the complex fprintf().

Introduce a new fatal source RTEMS_FATAL_SOURCE_PANIC for rtems_panic()
and output via vprintk().

Update #3244.

cpukit/sapi/include/rtems/fatal.h

@@ -88,6 +88,18 @@ RTEMS_NO_RETURN RTEMS_INLINE_ROUTINE void rtems_fatal(
   _Terminate( fatal_source, error_code );
 }
 
+/**
+ * @brief Prints the specified message via printk() and terminates the system.
+ *
+ * @param[in] fmt The message format.
+ * @param[in] ... The message parameters.
+ *
+ * @see _Terminate().
+ */
+RTEMS_NO_RETURN void rtems_panic(
+  const char *fmt, ...
+) RTEMS_PRINTFLIKE( 1, 2 );
+
 /**
  * @brief Returns a text for a fatal source.
  *