POSIX leaves undefined the order of output if stderr is injected into stdout,
and in practice it differs on Windows (Linux buffers both streams separately,
Windows interleaves them as they arrive without buffering).
This should help testing on other platforms
If a line ended with a string's closing quote, or a newline escape, then
skipping over that line via IF/ELIF/ELSE would fail to count that line,
offsetting the rest of the file.
I have no idea why but for some reason 9829be1 changed *specifically*
`if_skip_to_else` to have incorrect behavior on string endings. The incorrect
behavior on newline escapes seems to have been here since the beginning.
Also added a test to check for both of those behaviors in both functions.
Honestly, it baffles me that nobody ever noticed. I didn't until I started
working on #395.
