Here's an algorithm for the conversion ability scores of existing
characters.

1. Reverse the effects of any exercise that boosts scores.
2. Reverse the effects of 1st-Edition racial adjustments.
3. Map the scores from old to new values, as follows:

(Exception, Priests and students of the old magic should convert
Wisdom on the Intelligence table, instead.)

Strength:
	3-7? -> +1
	8?-13 -> 10
	14-15 -> 11
	16 -> 12
	17 -> 13
	18 -> 14
	18.01-18.50 -> 15
	18.51-18.75 -> 16
	18.76-18.90 -> 17
	18.91-18.99 -> 18
	18.00 -> 19
	19 -> 20

Intelligence, Charisma:
	3-9 -> +1
	11-17 -> -1
	18 -> unchanged
	18.00 -> 20
	19 -> 22

Wisdom, Dexterity, Constitution:
	3-8 -> +1
	9-11 -> 10
	12-14 -> 11
	15 -> 12
	16 -> 14
	17 -> 16
	18 -> 18
	18.00 -> 19
	19 -> 20

With all these tables, each point beyond 19 is another +2 for this
conversion.

4. Apply 3rd-Edition racial adjustments.
5. Apply every-4th-level ability bonuses only to those abilities that
won't clash with character history if raised.
6. Boost scores with exercise, as desired (see top of section).