[css-values-4] Remove implication that calc(-0) produces a negative zero (CSS parsing removes the detail).

Author: tabatkins

css-values-4/Overview.bs

@@ -3454,22 +3454,16 @@ Type Checking</h3>
 
 	* Negative zero
 		(0⁻)
-		can be produced literally by negating a zero
-		(''-0''),
-		or by a multiplication or division that produces zero
+		can be produced by a multiplication or division that produces zero
 		with exactly one negative argument
-		(such as ''-5 * 0'' or ''1 / (-1 / 0)'').
-
-		Note: Note that,
-		outside of [=math functions=],
-		''-0'' just produces a "standard" zero,
-		identical to ''0''--
-		CSS as a whole doesn't recognize the concept of signed zeros.
-		Negative zeros also don't escape a [=math function=];
+		(such as ''-5 * 0'' or ''1 / (-1 / 0)''),
+		or by certain argument combinations in the other [=math functions=].
+
+		Note: Note that negative zeros don't escape a [=math function=];
 		as detailed below,
 		they're "censored" away into an "unsigned" zero.
-	* ''-0 + -0''
-		or ''-0 - 0''
+	* ''0⁻ + 0⁻''
+		or ''0⁻ - 0''
 		produces 0⁻.
 		All other additions or subtractions that would produce a zero
 		produce 0⁺.
@@ -3485,9 +3479,9 @@ Type Checking</h3>
 		follows standard sign rules.)
 	* When comparing 0⁺ and 0⁻,
 		0⁻ is less than 0⁺.
-		For example, ''min(0, -0)'' must produce 0⁻,
-		''max(0, -0)'' must produce 0⁺,
-		and ''clamp(0, -0, 1)'' must produce 0⁺.
+		For example, ''min(0⁺, 0⁻)'' must produce 0⁻,
+		''max(0⁺, 0⁻)'' must produce 0⁺,
+		and ''clamp(0⁺, 0⁻, 1)'' must produce 0⁺.
 
 	If a <dfn export>top-level calculation</dfn>
 	(a [=math function=] not nested inside of another [=math function=])