Removed printf call in _Error_Handler() to reduce code size

By using the printf function of the library C this inflates
the size of the code. An alternative, will be to implement
a tiny and limited functionality implementation of printf.

Example, build modified Blink.ino with _Error_Handler()
calls for Nucloe F103RB:
With printf: Sketch uses 16368 bytes
Without printf: Sketch uses 10220 bytes
Difference is 6k of flash used which is not negligible.
Nano static library is linked to use this printf call.

Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Author: fpistm

cores/arduino/stm32/stm32_def.c

@@ -12,7 +12,13 @@ extern "C" {
 WEAK void _Error_Handler(const char * msg, int val)
 {
   /* User can add his own implementation to report the HAL error return state */
-  printf("Error: %s (%i)\n", msg, val);
+  /* By using the printf function of the library C this inflates the size of
+   * the code, use a lot of stack. An alternative, will be to implement a tiny
+   * and limited functionality implementation of printf.
+   */
+  UNUSED(msg);
+  UNUSED(val);
+  /*printf("Error: %s (%i)\n", msg, val);*/
   while(1)
   {
   }