Add CIDR support for expr

[KujouRinka]

I add CIDR support for expr. Here's example:

- name: block cidr
  action: block
  expr: cidr(string(ip.dst), "192.168.0.0/16")

I use Patch to parse CIDR string at expr compile time, for this avoids the use of lock and repeated parsing of the CIDR string.

[tobyxdd]

Much appreciated!