[8u60] RFR: 8078470: [Linux] Replace syscall use in os::fork_and_exec with glibc fork() and execve()

[David Holmes]

webrev: http://cr.openjdk.java.net/~dholmes/8078470/webrev/

bug: https://bugs.openjdk.java.net/browse/JDK-8078470

For historical reasons, dating back to LinuxThreads, os::fork_and_exec 
uses direct syscalls to perform fork and execve functions. The fork 
syscall has been deprecated on linux for quite some time and some 
distributions are now shipping with deprecated syscalls removed - this 
results in a ENOSYS error and the "OnError" commands that utilize 
os::fork_and_exec no longer work.

The problem was discussed here:

http://mail.openjdk.java.net/pipermail/hotspot-dev/2015-April/017916.html

It seems the concerns surrounding direct use of glibc fork() and exec() 
are no longer legitimate and Martin Buchholz reports that Google 
replaced the syscalls with glibc calls some time ago and have not had 
any problems. So we propose to apply the same change uniformly on Linux.

This is initially going into 8u60 via jdk8u-hs-dev due to time 
constraints on the 8u60 schedule, and an internal limitation preventing 
me from pushing this to 9 right now. But it will be "backported" to 9 ASAP.

Thanks,
David