Dial code normalizer

Clean up phone numbers typed into a sign-up form by converting each one to international E.164 form (+ followed by the country calling code and the national number), or saying why it cannot be converted.

Three countries are supported:

Process each entry in this order:

1. Remove every space, -, ., ( and ). What remains must be digits, optionally preceded by one +. Any other character (a letter, a + anywhere but the first position, ...) gives reject:bad-chars.
2. International form: the entry starts with +, or with 00 (which acts like +). The digits after that marker must begin with one of the three calling codes, otherwise reject:unknown-country (this includes nothing following the marker). The digits after the calling code are the national number; for GB and FR a single 0 at its front is a trunk prefix typed by mistake, as in +44 (0) 20 ..., and is dropped. For US nothing is dropped.
3. National form (anything else): the number belongs to the default_country. For US, if there are exactly 11 digits and the first is 1, that 1 is dropped. For GB and FR, a single leading 0 is dropped if present.
4. The national number must now have the exact length from the table, otherwise reject:bad-length. Then, for US numbers only, its first digit must be 2 to 9, otherwise reject:bad-area.

A valid entry becomes "+", the calling code, and the national number. Only the first failing check is reported.

Input: default_country, one of "US", "GB", "FR"; and numbers, a list of strings.

Output: a list with one string per entry of numbers, in the same order: the E.164 number or the reject:... reason.