Reverted change for weak loop() binding.

Added Arduino compatible serialEventRun according to review comment (instead).

Author: dok-net

Diff for: cores/esp32/HardwareSerial.h

@@ -97,6 +97,8 @@ class HardwareSerial: public Stream
     uart_t* _uart;
 };
 
+extern void serialEventRun(void) __attribute__((weak));
+
 #if !defined(NO_GLOBAL_INSTANCES) && !defined(NO_GLOBAL_SERIAL)
 extern HardwareSerial Serial;
 extern HardwareSerial Serial1;

Diff for: cores/esp32/main.cpp

@@ -9,19 +9,15 @@ TaskHandle_t loopTaskHandle = NULL;
 
 bool loopTaskWDTEnabled;
 
-extern "C" void esp_loop(void) __attribute__((weak));
-extern "C" void esp_loop(void) {
-    loop();
-}
-
 void loopTask(void *pvParameters)
 {
     setup();
     for(;;) {
         if(loopTaskWDTEnabled){
             esp_task_wdt_reset();
         }
-        esp_loop();
+        loop();
+        if (serialEventRun) serialEventRun();
     }
 }