Fix backslash cr nl bug

[MeGaGiGaGon]

Description

This fixes another one of the hypothesis errors. It took me a long time to track down, but it was again in this translation layer:

Since transform_whitespace only checked for \\\n, any \\\r\n whitespace token would break everything. This is because since the offset adjustments never happened, on the token after the \\\r\n there would be a position mismatch, triggering the code to add a \n to the prefix of that token. This is fine for the first pass, but after getting converted to code this causes the second pass to crash.
Input Code:

x=\<carriage return><newline>
1

After first pass:

x=<newline>
1

Crashes on second pass due to invalid code.

I also included the \\\r check for completeness, since even though code with \\\r seemed to work before it sounded to me like a bug waiting to happen, and has not caused any test failures (at least for me when running the tests locally).

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?
  • N/A crash fix, no docs changed