Redirect _write to Serial.

Former-commit-id: 724eab0

Author: h2zero

cores/nRF5/libc/printf/putchar.cpp

@@ -1,10 +1,21 @@
 #include "Arduino.h"
 #include "printf.h"
 
-extern "C" void _putchar(const char c)
+extern "C"
+{
+
+void _putchar(const char c)
 {
     if(c == '\n') {
         Serial.write('\r');
     }
     Serial.write(c);
 }
+
+int _write (int fd, const void *buf, size_t count)
+{
+  (void) fd;
+  return (int)Serial.write((const uint8_t*)buf, count);
+}
+
+} //extern "C"