Parsing char8_t, char16_t, char32_t and wchar_t

[VladimirShaleev]

Parsing incoming Unicode strings

For example, if we have an incoming line with an incorrect character in the ip addresses, for example:

ipv4_address::parse(u8"127.\ud55c.\U00010348.1")

In the exception we should receive the following message:

try {
    ipv4_address::parse(u8"127.\ud55c.\U00010348.1");
} catch (const std::exception& exc) {
    std::cout << exc.what() << std::endl;
    // unexpected unicode symbol {U+D55C} in address 127.{U+D55C}.{U+10348}.1
}