[Z3] Update Float >> toBitVector: to work also on Smalltalk/X

This commit updates `Float >> toBitVector:` to work on both Pharo and
Smalltalk/X.

The code is arguably ugly but I did not find a nicer way to do it. One
cannot simply force "Pharo way" on Smalltalk/X and make `#basicAt:`
behaving the same - this would break existing code.

Another way would be to have some "new" compatibility method, but then,
where to place it? To `Z3-FFI-Pharo` and `Z3-FFI-SmalltalkX`? Did not
feel right - this has nothing to do with FFI.

Yet another way would be revert back and use of `asIEEE64BitWord`, and
implement this in both Smalltalk/X and "our" Pharo 8. This would break
`FloatingPoint` on stock Pharo 8 (but perhaps that's okay).

So in the end, I opted for this ugly "dialect" test and keep the ugliness
local to this method.

Author: janvrany

src/Z3/Float.extension.st

@@ -4,8 +4,29 @@ Extension { #name : #Float }
 Float >> toBitVector: length [
 	"Return the receiver as IEEE 754 bits"
 
-	^ ((self basicAt: 1) bitShift: 32) + (self basicAt: 2)
-				toBitVector: length.
+	| bits |
+
+	length = 64 ifFalse: [ self error: 'bit length mismatch' ].
+
+	"Following code is arguably ugly - but that's the cost of supporting 
+	 multiple Pharo versions and Smalltalk/X."
+
+	((Smalltalk respondsTo: #isSmalltalkX) and: [ Smalltalk isSmalltalkX ]) ifTrue: [ 
+		"This is Smalltalk/X:"
+		bits := 0.
+		UninterpretedBytes isBigEndian ifTrue: [ 
+			1 to: (length // 8) do: [:i | bits := (bits << 8) | (self basicAt: i) ]
+		] ifFalse: [ 
+			(length // 8) downTo: 1 do: [:i | bits := (bits << 8) | (self basicAt: i) ]
+		].
+	] ifFalse: [
+		"Assuming some version of Pharo:"
+		bits := ((self basicAt: 1) bitShift: 32) + (self basicAt: 2)
+	].
+
+	^ bits toBitVector: length
+
+	"Created: / 17-09-2025 / 12:21:38 / Jan Vrany <jan.vrany@labware.com>"
 ]
 
 { #category : #'*Z3' }