user submit code including null character causes incomplete output in pipe mode

[leoyuholo]

When user submit code like

#include <stdio.h>
int main() {
    printf("b4 null %c should be in the same output as b4 null\n", 0);
    return 0;
}

it causes output to be split into two in pipe mode

{ result: [ 'OK', 'OK' ],
  execute_time: 0.030843,
  memory_usage: 102400,
  compile_message: '',
  stdout:
   [ 'b4 null ',
     ' should be in the same output as b4 null\n',
     'b4 null ',
     ' should be in the same output as b4 null\n' ],
  stderr: [ '', '' ],
  total_time: 3.021,
  user: '17 print null' }

[leoyuholo]

added the test case described above pull request #2