fix compiler warning

This fix is to eliminate:

    full_stats.c:134:10: warning: passing argument 1 of 'get_testable_functions' from incompatible pointer type
    full_stats.c:134:68: warning: incompatible pointer types passing 'unsigned long *' to parameter of type 'size_t *' (aka 'unsigned int *') [-Wincompatible-pointer-types]