loosen comparison a little more for references

if 2 references are the same except for their fallback texts,
which differ only by one having a [] suffix while the other has not,
then they are considered as the same.
remove `NL` preceding blocks (in `normalise_md`)
Always use the fallback text when outputing markdown for references
loosen `loose_compare` for code blocks

if 2 code blocks only differ by a `\n` at the end of one of them,
then they are considered the same.