Workaround clang and ccache bugs described in http://petereisentraut.blogspot.co.il/2011/05/ccache-and-clang.html

 * Support for both in-source and out-of-source builds
 * Set library version to 0.12 to map Debian package
 * Add separate options to build tests, examples and documentation
 * Add pkgconfig lookup support (if installed with `make install`)
 * Add CMake lookup support (if isntalled with `make install`)
 * Add Google Test Source lookup
 * Add CTest support for running tests (use `make test` or `ctest -V`)

With the implementation of the more elaborate benchmarking
suite at https://github.com/miloyip/nativejson-benchmark,
the thirdparty performance tests are superseded.