* Change required to prevent a trailing space at the end of a separate module being propagated
* Detect the start of the output file rather than the start of the input file when deciding whether to output preceding snippets - this stops unnecessary whitespace and blank lines from being inserted when spans and statements are output in an order other than that from the input file.
* Add code to prevent space from being added with the prefix snippet if a) the snippet is entirely horizontal whitespace, or b) the snippet contains whitespace followed by a newline. This prevents trailing spaces at the end of a line from being added.
* Tests for this issue
* Tidy up `match` statements
* Add test with blank lines between `use` statements
