gcc-4.7/v0.1.6

Make option for build migration tool

- Add option BUILD_MKSANDWICH. By default build of migration tool
  is turned on.
- Add for option BUILD_TESTING help text and make it boolean.
- gtest dependency required only when tests are built.

gcc-4.7/v0.1.5

• removed useless template parameter defaults in specialization of SandwichDB (issue #7, static analysis by Coverity)
• fix -Wconversion warnings (issue #13)
• fix SandwichDB move ctor (issue #14)

gcc-4.7/v0.1.4: txn_db: fix commit()

• fix TxnDB::commit()

gcc-4.7/v0.1.3

• TxnDB::commit doesn't try to write empty batch

gcc-4.7/v0.1.2: fix walker moving forward after delete

• fix building with GTEST_SOURCE specified (issue #4).
• WIP: fix issue #5 that exposed as not moving walker from existing element after deleting some other.

minor release for re-licensing

• re-licensed under Apache 2.0 for LG Electronics
• minor fix issue #3 (sandwich/sequence overflow)

First potentially usable release

Should be suitable for webOS DB8

v0.1 specially for gcc 4.7.x compilers

Merge branch 'gcc-4.8' into gcc-4.7

Conflicts:
	include/leveldb/txn_db.hpp
	include/leveldb/whiteout_db.hpp