RFR(S): downport 8211326: add OS user related information to hs_err file

[Lindenmaier, Goetz]

Hi,

I would like to downport 8211326. It helps us maintain systems
that are (and most will be) running on jdk11.

Unfortunately, in posix.hpp the context changed slightly, and thus
the change does not apply. So I need a review.
Webrev against jdk11u:
http://cr.openjdk.java.net/~goetz/wr18/8211326-hs_err-user-jdk11u/01/
Original webrev:
http://cr.openjdk.java.net/~mbaesken/webrevs/8211326.4/

Best regards,
  Goetz.