Cherry-pick jemalloc nodump allocator for block cache, and ffi_try! fixing (#334)

* Adding jemalloc-nodump-allocator option for lru-cache (#328)

Adding LRUCacheOptions::set_no_dump_allocator, so we can use JemallocNoDumpAllocator of rocksdb to exclude some LRU Cache, like block cache, from core dump.