Add blank lines in default programs

[navzam]

Adds an extra blank line in the default C and C++ programs before the return statements, to help users insert code more easily.

The previous default for C was:

#include <stdio.h>
#include <kipr/wombat.h>

int main()
{
  printf("Hello, World!\n");
  return 0;
}

and now it's:

#include <stdio.h>
#include <kipr/wombat.h>

int main()
{
  printf("Hello, World!\n");

  return 0;
}