[8u] RFR 8208715: Conversion of milliseconds to nanoseconds in UNIXProcess contains bug

[Guo, James]

Hi,

Original bug:
     https://bugs.openjdk.java.net/browse/JDK-8208715
     https://hg.openjdk.java.net/jdk/jdk/rev/41257a58a588
        
Original patch does not apply cleanly to 8u:
        1. java.base/unix doesn't exist. I had to move the change of java.base/unix/classes/java/lang/ProcessImpl.java 
to solaris/classes/java/lang/UNIXProcess.java to make the patch work in Unix.
        2. Due to the conflict in test/java/lang/ProcessBuilder/Basic.java, I had to replace the testcase that checks 
Process.waitFor(timeout, TimeUnit.MILLISECONDS) with the one in 12u[1] and add a millisElapsedSince(long startNanoTime) method for it.
        
8u webrev:
     http://cr.openjdk.java.net/~alvdavi/webrevs/8208715/webrev.8u.00/
        
Testing: x86_64 build, affected tests [2], tier1
        
Thanks,
James Guo
        
[1] http://hg.openjdk.java.net/jdk/jdk/file/41257a58a588/test/jdk/java/lang/ProcessBuilder/Basic.java#l2410
[2] https://bugs.openjdk.java.net/secure/attachment/78016/JI9056393.java