Fixes pharo-project#4701

Ansi says to use rounded rather than truncated :
```
5.6.2.16.Message: asInteger Synopsis
Answer an integer approximating the receiver.
Definition: <number>
Answer the result of sending #rounded to the receiver.
````

Changed to `rounded`, ran all the tests that seemed relevant, and added a testcase for the issue at hand.

Author: kasperosterbye

src/Kernel-Tests/MagnitudeTest.class.st

@@ -0,0 +1,8 @@
+"
+A MagnitudeTest is a test class for testing the behavior of Magnitude
+"
+Class {
+	#name : #MagnitudeTest,
+	#superclass : #TestCase,
+	#category : #'Kernel-Tests-Numbers'
+}

src/Kernel-Tests/NumberTest.class.st

@@ -7,6 +7,13 @@ Class {
 	#category : #'Kernel-Tests-Numbers'
 }
 
+{ #category : #test }
+NumberTest >> testAsInteger [
+	self assert: 0.5 asInteger equals: 1.
+	self assert: (1/2) asInteger equals: 1
+	
+]
+
 { #category : #tests }
 NumberTest >> testFractionPart [
 

src/Kernel/Number.class.st

@@ -266,7 +266,7 @@ Number >> asFloat [
 Number >> asInteger [
 	"Answer an Integer nearest the receiver toward zero."
 
-	^self truncated
+	^self rounded
 ]
 
 { #category : #converting }