Command line argument parsing

A deploy tool reads its own argument vector rather than pulling in a parser. Scan argv left to right. A token that is exactly "--" closes option scanning, and every token after it is a plain argument. Until then: a token starting with "--" is a long option, where "--name=value" splits on its first "=" only (the value may be empty) and "--name" alone is worth "true"; a token starting with a single dash and holding at least one more character is a bundle whose every remaining character is a switch worth "true". Anything else, a lone "-" included, is a plain argument and sets nothing. Setting a name twice keeps the newer value at the older position. Return one "name=value" string per distinct name, ordered by where each name first appeared.