Replacing the old regex implementation

by Gábor Kövesdán for FreeBSD

The regex implementation in FreeBSD's libc is quite outdated. It is not developed any more, it is slow and it does not support wide characters. We need a modern version with better I18N support, good performance and standard-compliance. The work that has been done on grep also showed that there is quite much to optimize in this area. This project pretends to port the TRE regex implementation and apply some compatibility/optimization changes to suit better our needs.