Implement support to inspectFile operator into libmodsecurity

[zimmerle]

Operator inspectFile needs to be implemented inside libmodsecurity.

The documentation of the operator can be found here:
https://github.com/SpiderLabs/ModSecurity/wiki/Reference-Manual#inspectFile

The file already exist in the repository:
https://github.com/SpiderLabs/ModSecurity/blob/libmodsecurity/src/operators/inspect_file.cc

[zimmerle]

As of: 1866a3a @inspectFile is fully workable.