RFR: [11u, 12u] JDK-8170639: [Linux] jsig is limited to a maximum of 64 signals

[Ao Qi]

Hi,

I'd like to backport this change to 11u and 12u:

Original JBS:
  https://bugs.openjdk.java.net/browse/JDK-8170639

Original change:
  http://hg.openjdk.java.net/jdk/jdk/rev/3086f9259e97
(http://cr.openjdk.java.net/~aoqi/8170639/webrev.03/)

Original review threads:
  https://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2018-December/031839.html
  https://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2019-March/032909.html

Patch does not apply cleanly, because of minor changes in
os::Posix::init_2(void) introduced by JDK-8194860.

12u change:
  http://cr.openjdk.java.net/~aoqi/8170639/webrev.12u.03/

Tested: linux-x86_64-{server, minimal, zero}-{release, fastdebug}
build, solaris-x86_64-server-release build,
linux-mips64el-zero-release build, linux-x86_64-server-release tier1

May I also request to backport this fix to 11u?
http://cr.openjdk.java.net/~aoqi/8170639/webrev.12u.03 apply to
jdk11u-dev cleanly.

jdk11u-dev tested: linux-x86_64-{server, minimal, zero}-{release,
fastdebug} build, solaris-x86_64-server-release build,
linux-x86_64-server-release tier1

Thanks,
Ao Qi