Adding GNU/kFreeBSD support. As requested here:
http://code.google.com/p/leveldb/issues/detail?id=38

Use uint64_t instead of size_t in MemEnvTest. As pointed out at
http://code.google.com/p/leveldb/issues/detail?id=41

- LevelDB patch for FreeBSD. This resolves Issue 22.
  Contributed by dforsythe (thanks!).

- Removing Chromium-specific files.
  They are now going to live in the Chromium repository.

- Adding a benchmark page comparing LevelDB performance
  to SQLite and Kyoto Cabinet's TreeDB, along with
  code to generate the benchmarks.
  Thanks to Kevin Tseng for compiling the benchmarks,
  and Scott Hess and Mikio Hirabayashi for their
  help and advice.



git-svn-id: https://leveldb.googlecode.com/svn/trunk@40 62dab493-f737-651d-591e-8d6aee1b9529

git-svn-id: https://leveldb.googlecode.com/svn/trunk@35 62dab493-f737-651d-591e-8d6aee1b9529

This revision adds two major changes:
1. build_detect_platform which generates build_config.mk
   with platform-dependent flags for the build process
2. /port/atomic_pointer.h with anAtomicPointerimplementation
   for platforms without <cstdatomic>

Some of this code is loosely based on patches submitted to the 
LevelDB mailing list at https://groups.google.com/forum/#!forum/leveldb
Tip of the hat to Dave Smith and Edouard A, who both sent patches.

The presence of Snappy (http://code.google.com/p/snappy/) and
cstdatomic are now both detected in the build_detect_platform
script (1.) which gets executing during make.

For (2.), instead of broadly importing atomicops_* from Chromium or
the Google performance tools, we chose to just implement AtomicPointer 
and the limited atomic load and store operations it needs. 
This resulted in much less code and fewer files - everything is 
contained in atomic_pointer.h.



git-svn-id: https://leveldb.googlecode.com/svn/trunk@34 62dab493-f737-651d-591e-8d6aee1b9529