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/sendmail/Makefile

@@ -37,13 +37,11 @@ include $(TOPDIR)/Make.defs
 
 # Sendmail SMTP Example
 
-APPNAME = sendmail
+PROGNAME = sendmail
+PRIORITY = SCHED_PRIORITY_DEFAULT
+STACKSIZE = 2048
+MODULE = $(CONFIG_EXAMPLES_SENDMAIL)
 
 MAINSRC = sendmail_main.c
 
-CONFIG_XYZ_PROGNAME ?= sendmail$(EXEEXT)
-PROGNAME = $(CONFIG_XYZ_PROGNAME)
-
-MODULE = CONFIG_EXAMPLES_SENDMAIL
-
 include $(APPDIR)/Application.mk

examples/sendmail/sendmail_main.c

@@ -106,11 +106,7 @@ static const char g_msg_body[]  = CONFIG_EXAMPLES_SENDMAIL_BODY "\r\n";
  * Name: sendmail_main
  ****************************************************************************/
 
-#ifdef BUILD_MODULE
 int main(int argc, FAR char *argv[])
-#else
-int sendmail_main(int argc, char *argv[])
-#endif
 {
   struct in_addr addr;
 #if defined(CONFIG_EXAMPLES_SENDMAIL_NOMAC)