RFR 8172514: Stop checking for duplicate packages in the JVM_DefineModule() package list

[harold seigel]

Hi,

Please review this JDK-10 fix to removing checking for duplicate 
packages in the package list passed to JVM_DefineModule().  The checking 
is potentially expensive and also redundant because the JDK makes the 
same check.

Open webrev: 
http://javaweb.us.oracle.com/~hseigel/webrev/bug_8172514/webrev/index.html

JBS Bug: https://bugs.openjdk.java.net/browse/JDK-8172514

The fix was tested with the JCK lang and vm tests, the JTreg hotspot, 
java/io, java/lang, java/util and other tests, the RBT tier2 -tier5 
tests, the co-located and non-colocated NSK tests, and with JPRT.

Thanks, Harold