Q:

Does "old" literally mean "old" in this context, or is it an intensifier?

    "Haven't I told you he's not going?" he hissed. "He's
going to Stonewall High and he'll be grateful for it. I've read those
letters and he needs all sorts of rubbish –– spell books and wands and
––"        "If he wants ter go, a great Muggle like you
won't stop him," growled Hagrid. "Stop Lily an' James Potter's son
goin' ter Hogwarts! Yer mad. His name's been down ever since he was
born. He's off ter the finest school of witchcraft and wizardry in the
world. Seven years there and he won't know himself. He'll be with
youngsters of his own sort, fer a change, an' he'll be under the
greatest headmaster Hogwarts ever had Albus Dumbled––"
    "I AM NOT PAYING FOR SOME CRACKPOT OLD FOOL TO
TEACH HIM MAGIC TRICKS!" yelled Uncle Vernon. (Harry Potter and the
Sorcerer's Stone)

Old is used as an intensifier, say these websites: Webster's #5; Wiktionary #12. So I guess the example's old has the meaning after an adjective crackpot. But I’m not sure, ‘cause the websites seem to kind of restrict the boundary of the use. Can old be used as an intensifier after all sorts of adjectives or adjective phrases?

A:

I think old has a literal meaning.
This definition seems closest.

c :  of long standing 

In other words the person has been a fool for a very long time, long enough to prove that that's all he'll ever be.

