Consolidate OVAL/string comparison. Delete weaker code.
Consolidate OVAL/string comparison. Delete weaker code.

Previously we had two implementations of string comparison.
The implementation from OVAL Results model is slightly different
to this removal, however the differences don't look to be material.

Hexadorsimal/openscap,isimluk/openscap,OpenSCAP/openscap,isimluk/openscap,OpenSCAP/openscap,jan-cerny/openscap,postfix/openscap,redhatrises/openscap,redhatrises/openscap,mpreisler/openscap,OpenSCAP/openscap,mpreisler/openscap,openprivacy/openscap,jan-cerny/openscap,OpenSCAP/openscap,ybznek/openscap,postfix/openscap,redhatrises/openscap,ybznek/openscap,mpreisler/openscap,jan-cerny/openscap,Hexadorsimal/openscap,postfix/openscap,Hexadorsimal/openscap,isimluk/openscap,Hexadorsimal/openscap,openprivacy/openscap,openprivacy/openscap,OpenSCAP/openscap,Hexadorsimal/openscap,isimluk/openscap,postfix/openscap,redhatrises/openscap,mpreisler/openscap,jan-cerny/openscap,ybznek/openscap,Hexadorsimal/openscap,mpreisler/openscap,jan-cerny/openscap,mpreisler/openscap,postfix/openscap,postfix/openscap,openprivacy/openscap,OpenSCAP/openscap,redhatrises/openscap,ybznek/openscap,isimluk/openscap,openprivacy/openscap,isimluk/openscap,redhatrises/openscap,ybznek/openscap,openprivacy/openscap,ybznek/openscap,jan-cerny/openscap