querystring: fix unescape override

Documentation states that `querystring.unescape` may be overridden to
replace unescaper during parsing. However, the function was only
being used as a fallback for when the native decoder throws (on a
malformed URL). This patch moves the call to the native function and
the try/catch around it into querystring.unescape then has the parser
always invoke it, so that an override will always be used.

Fixes #4055

Reviewed-By: Fedor Indutny <fedor@indutny.com>
url: Add support for RFC 3490 separators

There is no need to split the host by hand in `url.js` – Punycode.js
takes care of it anyway. This not only simplifies the code, but also
adds support for RFC 3490 separators (i.e. not just U+002E, but U+3002,
U+FF0E, and U+FF61 as well).

Closes #6055.

Reviewed-By: Fedor Indutny <fedor@indutny.com>
Merge remote-tracking branch 'upstream/v0.10' into v0.10