getinmemory: make the example easier to follow

1. Remove the comment warning that it's "not been verified to work". It
   works with no problems in my testing.

2. Remove 2 unnecessary includes.

3. Remove the myrealloc(). Initialize chunk.memory with malloc() instead
   of NULL. The comments for these two parts contradicted each other.

4. Handle out of memory from realloc() instead of continuing.

5. Print a brief status message at the end.