Fix Issue 13273 - ddoc can't handle \r in unittests and ESCAPES properly

https://issues.dlang.org/show_bug.cgi?id=13273

Simple fixes for documented unittest and ESCAPES in a .ddoc file when using `\r\n?` line endings.

Without these, the `compilable/ddoc*` dmd tests fail on my Windows setup, because Git checks out the files with `\r\n` line endings. This is the default Git behaviour now, presumably the autotester is **not** doing this, and it should (how to fix that?).

I haven't added any tests, because the needed tests (`ddocunittest.d` and `ddoc9369.d`) are already present! (see above)