Fix: eatNargs() for 'opt.narg === 0' and boolean typed options

[juergba]

Description

Currently the parser handles opts.narg before opts.array and therefore eatArray() is not restricted by the opts.narg value.

The edge case opt.narg === 0 is handled in a different way since checkAllAliases() returns false instead of value 0. Case opt.narg === 0 should be handled the same way as opt.narg > 0 to keep the distinction between opts.narg and opts.array options clear and clean.

Description of Change

• checkAllAliases(): fixes case of opt.narg === 0 and returns now 0 instead of false
• eatNargs(): sets now default values in case of opt.narg === 0

Note: the default value of a string typed option is currently an empty string (defaultForType()).
I would have expected undefined.