options.parse(argc, argv) modifies argv

[vladimirgamalyan]

(enhancement, feature request) Some times command line arguments are also passed to other libs (for example to doctest), so it would be better to have void Options::parse(int argc, const char* const* argv); signature, to ensure that argv will not be modified. Another case - unit tests, where now we have to copy string literals to r/w buffer before passing to Options::parse.