Patches not processed correctly

[tekkac]

Description

When displaying a solution with the command python starklings.py -s path/to/exercise.cairo, mid-file changes are applied one line above the actual changes which can break solutions. This looks like an off-by-one issue in the patch library used in src/solutions.py

Acceptance criteria

• Patching an exercise file should give the same output as patch exercise.cairo solution.cairo -o -

[Bernardstanislas]

@tdelabro I take it since I include it in the work of generating the solutions upon binary build using hooks