Adding support for Linux-ppc64.
dding support to download native snappy source code using git.

Usage Example:
make USE_GIT=true GIT_REPO_URL=https://git_repo/snappy GIT_SNAPPY_BRANCH=origin/my-branch/snappy-1.1.0
Adding support for compiling with IBM JDK.
Only IBM JDK 7 needs the edited header files. IBM JDK 6 is able to work with the default ones.
Merge pull request #70 from jwang302/develop

Adding support of Linux-ppc64, IBM JDK and using git mirrors for native snappy.