Allocate some memory
char *SLcalloc (unsigned int num_elem, unsigned int elem_size)
This function uses calloc to allocate memory for
num_elem objects with each of size elem_size and returns
the result. In addition, the newly allocated memory is zeroed.
Upon error it returns NULL; otherwise it returns a pointer to
the allocated memory. One should use SLfree to free the
memory after used.
SLmalloc, SLrealloc, SLfree