The AST structures track annotations (e.g., at the moment, source code
position information) in a lot of places. This patch tidies up a bit and
removes some duplication, ensuring a single level of annotation wrapping
at each AST recursion level.
This will be important when adding type information in these
annotations, because there will be consitency constraints to be ensured
and duplication is a likely source of mistakes.
this patch is just a bunch of `sed` commands
```shell
cd compiler
sed -i 's/Pos.marked/Marked.pos/g' *.ml* **/*.ml*
sed -i 's/Pos.unmark/Marked.unmark/g' *.ml* **/*.ml*
sed -i 's/Pos\.get_position/Marked.get_mark/g' *.ml* **/*.ml*
sed -i 's/Pos\.same_pos_as/Marked.same_mark_as/g' *.ml* **/*.ml*
sed -i 's/Pos\.map_under_mark/Marked.map_under_mark/g' *.ml* **/*.ml*
sed -i 's/Pos\.mark/Marked.mark/g' *.ml* **/*.ml*
sed -i 's/Pos\.compare_marked/Marked.compare/g' *.ml* **/*.ml*
```
This avoids many intermediate calls to e.g. `Format.asprintf`; should result in
some cases in "more correct" use of `Format`¹, avoid the computation of unused
debug strings, and make the code more readable.
¹ for `Format` to work as expected, all intermediate calls need to go through
it. Some cases of formatting to an intermediate string then printing through Format
again are still present, but this makes the situation better.
