Make delay() as overridable as yield() already is, and add overridable loop_end() (#6306)

* Make delay() overridable "weak"

* Add pluggable loop_end()

* Release tag 5.2.3 for SoftwareSerial

Author: dok-net

cores/esp8266/core_esp8266_main.cpp

@@ -121,6 +121,14 @@ extern "C" void optimistic_yield(uint32_t interval_us) {
     }
 }
 
+extern "C" void __loop_end (void)
+{
+    run_scheduled_functions();
+    run_scheduled_recurrent_functions();
+}
+
+extern "C" void loop_end (void) __attribute__ ((weak, alias("__loop_end")));
+
 static void loop_wrapper() {
     static bool setup_done = false;
     preloop_update_frequency();
@@ -129,8 +137,7 @@ static void loop_wrapper() {
         setup_done = true;
     }
     loop();
-    run_scheduled_functions();
-    run_scheduled_recurrent_functions();
+    loop_end();
     esp_schedule();
 }
 

cores/esp8266/core_esp8266_wiring.cpp

@@ -43,7 +43,7 @@ void delay_end(void* arg) {
     esp_schedule();
 }
 
-void delay(unsigned long ms) {
+void __delay(unsigned long ms) {
     if(ms) {
         os_timer_setfn(&delay_timer, (os_timer_func_t*) &delay_end, 0);
         os_timer_arm(&delay_timer, ms, ONCE);
@@ -56,6 +56,8 @@ void delay(unsigned long ms) {
     }
 }
 
+void delay(unsigned long ms) __attribute__ ((weak, alias("__delay"))); 
+
 void micros_overflow_tick(void* arg) {
     (void) arg;
     uint32_t m = system_get_time();