Fix a compiling error for some certain gcc versions.

Merge pull request #7 from pei-jikui/init

Init the operator before using it to avoid some compiling errors.

prioritized multiple logic operators computation are supported.

multiple prioritized logic operators supported

multiple logic operators are supported

support up to 5 logic operators in one if condition. The limitation of 5 is duo to the stack size of the script engine is 10.

if (a || b && c || d || e && f) {
}

Doesn't support the priority of the operators. The value is computed in order from left to right.

We will try to support the priority later.

nginx if condition enhancement

support simply logic computation for if directive such as if (a || b) , if (a &&b). Planning to support more complicated logic computation such as if (a && (b || c)) etc ..