Log Message:
Update to version 20120726.

Major changes:
- Introduce SIGHUP reloading.
- The symlink device can be enabled by '--enable-symlink-device' configure
  option.
- Fix the unknown error under some mutex condition.
- Fix the wrong reservation key handling.
- Use Clang as first choice compiler.
- Use _GNU_SOURCE on linux platform.

Current Limitations of SIGHUP support:
- The parameters other than PG, IG, and LU are not reloaded by SIGHUP.
- PG and IG mapped to LU can't be deleted by SIGHUP.
- If you delete an active LU, all connections of the LU are closed by
  SIGHUP.
- Can't modify LU by SIGHUP.
- Updating IG is not affected until the next login.