Added json_spirit package

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
json_spirit: Add semi-automatic update macro

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
json_spirit: Support shared builds

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
FIxup

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
json_spirit: Remove unneeded CMake switches

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
json_spirit: Add linking test

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
Merge pull request #476 from highperformancecoder/master

Add json_spirit package.