Merge branch 'jk/arith-expansion-coding-guidelines'

The coding guideline for shell scripts instructed to refer to a variable with dollar-sign inside arithmetic expansion to work around a bug in old versions of dash, which is a thing of the past. Now we are not forbidden from writing $((var+1)). * jk/arith-expansion-coding-guidelines: CodingGuidelines: drop arithmetic expansion advice to use "$x"