runnableExamples gives wrong values for number literals

[timotheecour]

Example

echo "ok0"
echo 0xffffffffffffffff
runnableExamples:
  echo "ok1"
  echo 0xffffffffffffffff

Current Output

nim doc main
ok0
-1
ok1
4294967295

Expected Output

ok0
-1
ok1
-1

Additional Information

• 1.5.1 f28dc2c
• originally reported to me by @xflywind
• the problem stems from fact that the generated file contains:
  /Users/timothee/git_clone/nim/timn/build/nimcache/runnableExamples/t11969_examples1.nim

echo "ok1"
echo 0xFFFFFFFF

• related but different: runnableExamples transforms do: => : and (expr) => expr, producing invalid code #13491
• probably different: parseHexInt doesn't check the value's length. #17208