fix db_sanity_test
Fix Autoroll logger

Summary:
If auto roll logger can't create a new LOG file on roll (if, for example, somebody deletes rocksdb directory while rocksdb is running, khm), we'll try to call Logv on invalid address and get a SIGSEGV. This diff will fix the issue

Here's the paste of the stack trace: https://phabricator.fb.com/P8276386 (fb-only)

Test Plan: make check is fine, although not really testing error condition

Reviewers: haobo, ljin, yhchiang

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17367
Minor fix in rocksdb jni library, RocksDB now does not implement Closeable.

Summary:
* [java] RocksDB now does not implement Closeable.
* [java] RocksDB.close() is now synchronized.
* [c++] Fix a bug in rocksjni.cc that does not release a java reference before
        throwing an exception.

Test Plan:
make jni
make jtest

Reviewers: haobo, sdong

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17355
[C-API] added the possiblity to create a HashSkipList or HashLinkedList to support prefix seeks
Fixed a compile error which tries to check whether a size_t < 0 in env_posix.cc

Summary:
Fixed a compile error which tries to check whether a size_t < 0 in env_posix.cc

util/env_posix.cc:180:16: error: comparison of unsigned expression < 0 is always false [-Werror,-Wtautological-compare]
    } while (r < 0 && errno == EINTR);
             ~ ^ ~
1 error generated.

Test Plan: make check all

Reviewers: igor, haobo

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17379
Merge pull request #105 from tecbot/c-api-prefix

[C-API] support prefix seeks