The current Roman Catholic definition of saint appears to be something like the following:
Most people use the word “saint” to refer to someone who is exceptionally good or “holy.” In the Catholic Church, however, a “saint” has a more specific meaning: someone who has led a life of “heroic virtue.” This definition includes the four “cardinal” virtues: prudence, temperance, fortitude and justice; as well as the “theological” virtues: faith, hope and charity. A saint displays these qualities in a consistent and exceptional way. When someone is proclaimed a saint by the pope – which can happen only after death – public devotion to the saint, called a “cultus,” is authorized for Catholics throughout the world. - Mathew Schmalz, Associate Professor of Religion, College of the Holy Cross
Very many of Paul's New Testament letters are addressed to "the saints in" whatever region. Many English translations insert a phrase, "called (to be) saints" in some of the letters but not all of them; one example of each is offered below:
To all that be in Rome, beloved of God, called to be saints: Grace to you and peace from God our Father, and the Lord Jesus Christ. - Romans 1:7
To the saints and faithful brethren in Christ which are at Colosse: Grace be unto you, and peace, from God our Father and the Lord Jesus Christ. - Colossians 1:2
Merely reading the greetings as they stand it appears that Paul either considered all believers to be saints or he considered them to be a category among living believers: Hence the phrases "and to the faithful" (Ephesians 1:1) and "with the bishops and deacons" (Philippians 1:1).
Going by the current Catholic definition of saint, which indicates that the title is only conferred (by a Pope) upon the deceased, one would have to deduce that Paul is including dead people in his address. Since this cannot possibly be the case it must be assumed that the Catholic definition of saint has changed over time.
I have two related questions: 1) When did the Roman Catholic definition of saint change and restrict this nomenclature only to the dead when Paul clearly applies the title to the living?, 2) Does this change or alter the way Paul's letters are read or does a modern Catholic ignore the Catholic definition when reading the New Testament? In other words, do modern Catholics parenthetically think something like "but not real saints" when reading these letters?