build: Use compile_time_request system for init, tasks, and shutdown

Avoid using linker magic to define the init, task, and shutdown
functions.  Instead, use the compile_time_request system.  This
simplifies the build and produces more efficient code.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/simulator/main.c

@@ -117,7 +117,7 @@ console_push_output(uint8_t len)
  ****************************************************************/
 
 // Periodically sleep so we don't consume all CPU
-static void
+void
 simu_pause(void)
 {
     // XXX - should check that no timers are present.