Make the description of the comp_simplify rule clearer

By changing the variable names we clarify that those are rules that can match.

Furthermore, we also change all occurrences of the very awkward "as long as possible" to "until a fixed point is reached".

mentioned in merge request !12 (closed)

added 2 commits

• 3b9e0708 - 1 commit from branch master
• 1ed650d8 - Make the description of the comp_simplify rule clearer

Compare with previous version

mentioned in commit 432c59c0

merged