Peter M. Groen / cxxopts

Fixes #356.

Make the usage displaying optional

Related to #339.

Fixes ##339

Move nodiscard before inline.

* Fixes #240: Multiple long option names / aliases

* We now use a vector of long option names instead of a single name
* When specifying an option, you can provide multiple names separated by commas, at most one of which may have a length of 1 (not necessarily the first specified name). The length-1 name is the single-hyphen switch (the "short name").
* Hashing uses the first long name
* Option help currently only uses the first long name.

…ded end-of-namespace comment (#351)

* Fixes #345, fixes #346, regards #340: Put exceptions in a sub-namespace and renamed them accordingly.

* Also fixed some "loose ends" regarding namespace indentation which were missing in PR #350.

* Dropped `required_option_missing` as it is unused.

Memory leak was caused by `exit`.

* Namespace no longer induce indentation
* Namespace opening brace now on same line as namespace name
* Namespace closing brace now has an empty line before it unless the namespace contents were short and with no empty lines
* Namespace closing brace now always followed by a comment with the closed namespace' name

* Solve `arguments()` showing empty keys when there is only a short option.

Ref #242. Adds an example in the example file showing the unmatched
arguments that are stored.

Fixes #324

Fixes 323. Adds a function to retrieve the program name.

* Add iterator (#126) and easily print-out (#223) to ParseResult

Fixes #312.

Fixes #311.

Fixes #303

Fixes #204.