The description of option case-sensitive belongs to case-insensitive

[chrullrich]

This is a sort of follow-up to #206; that bug was fixed in a way that increased confusion.

The 3.8 manual describes the case-sensitive option in terms of acro acting case-insensitively, i.e. accepting the ID of an acronym regardless of case.

This is not correct; the behavior of the option follows the usual meaning of its name rather than the description. With case-sensitive=true, a case mismatch between declaration and usage is an error.

The simplest fix for this is to exchange the descriptions of case-sensitive and case-insensitive.