Make tor_inet_pton() handle bad addresses consistently on Windows

tor_inet_pton() handles bad addresses differently on Windows and Linux/macOS.

For example, the address: "2000::1a00::1000:fc098" (two "::") fails this test on Windows, but succeeds on Linux and macOS: https://github.com/torproject/tor/pull/1831/commits/05f4f93722d46c0e8f1d09b4dea4bf5d1743d93f#diff-048243cd6d9ed36dda0944181d8ec8abR1729

Let's fix this bug and backport it.

In general, we should make all the functions in this file behave identically:

• zero any out parameters at the start of the function
• zero any out parameters on failure