Add an assert and avoid std::sort(autovector) to investigate an ASAN issue

Summary:
ASAN build fails once for this error:

14:04:52 ==== Test DBTest.CompactFilesOnLevelCompaction
14:04:52 db_test: db/version_set.cc:1062: void rocksdb::VersionStorageInfo::AddFile(int, rocksdb::FileMetaData*): Assertion `level <= 0 || level_files->empty() || internal_comparator_->Compare( (*level_files)[level_files->size() - 1]->largest, f->smallest) < 0' failed.

Not abling figure out reason. We use std:vector for sorting for save and add one more assert to help figure out whether it is the sorting's problem.

Test Plan: make all check

Reviewers: yhchiang, rven, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D30117
Added 'dump_live_files' command to ldb tool.

Summary:
Priliminary diff to solicit comments.
Given DB path, dump all SST files (key/value and properties), WAL file and manifest
files. What command options do we need to support for this command? Maybe
output_hex for keys?

Test Plan: Create additional ldb unit tests.

Reviewers: sdong, rven

Reviewed By: rven

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D29547
Optimize default compile to compilation platform by default

Summary:
This diff changes compile to optimize for native platform by default. This will automatically turn on crc32 optimizations for modern processors, which greatly improves rocksdb's performance.

I also did some more changes to compilation documentation.

Test Plan:
compile with `make`, observe -march=native
compile with `PORTABLE=1 make`, observe no -march=native

Reviewers: sdong, rven, yhchiang, MarkCallaghan

Reviewed By: MarkCallaghan

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30225
RocksDB: Allow Level-Style Compaction to Place Files in Different Paths

Summary:
Allow Level-style compaction to place files in different paths
This diff provides the code for task 4854591. We now support level-compaction
to place files in different paths by specifying  them in db_paths  along with
the minimum level for files to store in that path.

Test Plan: ManualLevelCompactionOutputPathId in db_test.cc

Reviewers: yhchiang, MarkCallaghan, dhruba, yoshinorim, sdong

Reviewed By: sdong

Subscribers: yoshinorim, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D29799