tls: using %StringSplit to split `cert.subjectaltname`

There are 2 changes in this patch:

* using `%StringSplit` not `StringSplitOnRegExp` in [v8/v8](https://github.com/v8/v8/blob/master/src/string.js#L588), the newer function seems to be faster.

* decreasing the times of comparing regular expression, and more readable for human.
Click https://www.openssl.org/docs/apps/x509v3_config.html#Subject_Alternative_Name_
> subjectAltName=email:copy,email:my@other.address,URI:http://my.url.here/

I just found there is not spaces in examples, but I try to fetch `subjectAltNames` of a certain number of tls servers, the result is comma+space as the delimiter, and does this indicate we are right totally? I don't know, do you have any sharing thoughts on this?