Added Zephir supports compile and link with external-libraries

Added `extra-libs` `extra-cflags` `package-dependencies` options to `config.json` . 

With `package-dependencies` options , we can declare libraries dependencies and version check by `pkg-config`
Syntax like `nodejs`'s `package.json`.
```
"package-dependencies": {
        "openssl": "*",
        "libpng": ">= 0.1.0",
        "protobuf": "<= 2.6.1"
    },
"extra-cflags": "-I/usr/local/Cellar/libevent/2.0.21_1/include",
"extra-libs": "-L/usr/local/Cellar/libevent/2.0.21_1/lib -levent"
``` 

Version compare operators now support `=`, `>=`, `<=`, and `version` can be `*` that mean `'>= 0.0.0'` .

Since Zephir have `optimizers` and `cblock` supports, with external-libraries supports, maybe we can using Zephir to writing drivers/wrappers/adaptors extensions to php.  :smile: 


Signed-off-by: Rack Lin <racklin@gmail.com>