Modified crypto_scrypt-sse to use emalloc

My system defaults to using the SSE variant which was still using either posix_memalign or malloc[not sure which path it was taking].

Consequently, it would ignore PHP's max memory limits and would not be reported for get_memory_usage

This change merely replaces the calls to malloc with emalloc.   I tried using safe_emalloc but kept getting segmentation faults.