Application.mk and main.c files: Change builtin's entry point from main to xxx_main by macro expansion. This change make the entry point fully compliant with POSIX/ANSI standard.

examples/netloop/lo_main.c

@@ -249,11 +249,7 @@ errout_with_socket:
  * Name: netloop_main
  ****************************************************************************/
 
-#ifdef BUILD_MODULE
 int main(int argc, FAR char *argv[])
-#else
-int netloop_main(int argc, char *argv[])
-#endif
 {
   pthread_t tid;
   int ret;