Go port of the PCRE library

The regular expression library PCRE (https://www.pcre.org/) has been transpiled from C to Go code.

This was done, by using c2go (https://github.com/elliotchance/c2go) to perform the majority of the work. Some manual refinement was performed, to fix some remaining errors and to be able to launch the tests with go test.

An API similar to the Go regex functions was added based on the Go C binding for pcre (https://github.com/gijsbers/go-pcre).