Take Keith's suggestion: rearrange `api/leveldb` by copyright to simplify maintenance of the license information.  Rename the "eleveldb" flavor to "basho" in the process, so the directory name matches the option.  List the choices in the configure help, and check for invalid flavors.

--HG--
rename : api/leveldb/util/perf_count.cc => api/leveldb/basho/perf_count.cc
rename : api/leveldb/include/leveldb/perf_count.h => api/leveldb/basho/perf_count.h
rename : api/leveldb/include/leveldb/replay_iterator.h => api/leveldb/hyperleveldb/replay_iterator.h
rename : api/leveldb/AUTHORS => api/leveldb/leveldb/AUTHORS
rename : api/leveldb/LICENSE => api/leveldb/leveldb/LICENSE
rename : api/leveldb/db/dbformat.h => api/leveldb/leveldb/db/dbformat.h
rename : api/leveldb/db/skiplist.h => api/leveldb/leveldb/db/skiplist.h
rename : api/leveldb/db/write_batch.cc => api/leveldb/leveldb/db/write_batch.cc
rename : api/leveldb/db/write_batch_internal.h => api/leveldb/leveldb/db/write_batch_internal.h
rename : api/leveldb/include/leveldb/cache.h => api/leveldb/leveldb/include/leveldb/cache.h
rename : api/leveldb/include/leveldb/comparator.h => api/leveldb/leveldb/include/leveldb/comparator.h
rename : api/leveldb/include/leveldb/db.h => api/leveldb/leveldb/include/leveldb/db.h
rename : api/leveldb/include/leveldb/env.h => api/leveldb/leveldb/include/leveldb/env.h
rename : api/leveldb/include/leveldb/filter_policy.h => api/leveldb/leveldb/include/leveldb/filter_policy.h
rename : api/leveldb/include/leveldb/iterator.h => api/leveldb/leveldb/include/leveldb/iterator.h
rename : api/leveldb/include/leveldb/options.h => api/leveldb/leveldb/include/leveldb/options.h
rename : api/leveldb/include/leveldb/slice.h => api/leveldb/leveldb/include/leveldb/slice.h
rename : api/leveldb/include/leveldb/status.h => api/leveldb/leveldb/include/leveldb/status.h
rename : api/leveldb/include/leveldb/write_batch.h => api/leveldb/leveldb/include/leveldb/write_batch.h
rename : api/leveldb/port/port.h => api/leveldb/leveldb/port/port.h
rename : api/leveldb/util/arena.h => api/leveldb/leveldb/util/arena.h
rename : api/leveldb/util/coding.cc => api/leveldb/leveldb/util/coding.cc
rename : api/leveldb/util/coding.h => api/leveldb/leveldb/util/coding.h
rename : api/leveldb/util/comparator.cc => api/leveldb/leveldb/util/comparator.cc
rename : api/leveldb/util/env.cc => api/leveldb/leveldb/util/env.cc
rename : api/leveldb/util/env_posix.cc => api/leveldb/leveldb/util/env_posix.cc
rename : api/leveldb/util/logging.cc => api/leveldb/leveldb/util/logging.cc
rename : api/leveldb/util/logging.h => api/leveldb/leveldb/util/logging.h
rename : api/leveldb/util/options.cc => api/leveldb/leveldb/util/options.cc
rename : api/leveldb/util/posix_logger.h => api/leveldb/leveldb/util/posix_logger.h
rename : api/leveldb/util/random.h => api/leveldb/leveldb/util/random.h
rename : api/leveldb/util/status.cc => api/leveldb/leveldb/util/status.cc