c33: weakly implement __cxa_pure_virtual to slim down build

Author: facchinm

Diff for: cores/arduino/main.cpp

@@ -134,3 +134,12 @@ extern "C" {
 
 //Declared weak in Arduino.h to allow user redefinitions.
 int atexit(void (*func)()) { return 0; }
+
+namespace __gnu_cxx {
+   void __verbose_terminate_handler() { }
+}
+extern "C" __attribute__((weak)) void __cxa_pure_virtual(void);
+extern "C" __attribute__((weak)) void __cxa_pure_virtual(void)
+{
+   exit(1);
+}