Add failing test

The cause of the test failure is confusion about
whether the architecture is 32 bit or 64 bit.

Author: owen-mc

go/ql/test/query-tests/Security/CWE-681/IncorrectIntegerConversion.expected

@@ -1,2 +1,3 @@
-failures
 testFailures
+| IncorrectIntegerConversion.go:497:15:497:15 | i | Unexpected result: hasValueFlow="i" |
+failures

go/ql/test/query-tests/Security/CWE-681/IncorrectIntegerConversion.go

@@ -491,3 +491,10 @@ func typeAssertion(s string) {
 	}
 
 }
+
+func dealWithArchSizeCorrectly(s string) uint {
+	if i, err := strconv.ParseUint(s, 10, 64); err == nil && i < math.MaxUint {
+		return uint(i)
+	}
+	return 0
+}