Improve URLExtensions.isIPv4/isIPv6

[st3fan]

In URLExtensions.swift we have isIPv4 and isIPv6 functions. The first uses a regex and the second just checks for the presence of a : in the string. Let's replace this with a call to inet_pton() to let the OS parse the address instead - delegating to a trusted OS function will be more robust.

Example at https://stackoverflow.com/questions/35056268/how-to-use-swift-convert-string-to-ipv6-addr

As part of this work, let's also start a URLExtensionsTests.swift in which we can test these two functions.

[dtee1]

Interested

[Tausifqureshi786]

Is someone still working on this issue?

[tommyming]

Hello, would like to know if this issue still opens? If yes I am interested to work on it, thanks.