[9] RFR 8074839: Resolve disabled warnings for libunpack and the unpack200 binary

[Mikael Vidstedt]

Please review the following change which fixes a number of native 
compilation warnings in the jdk.pack200 code.

Bug: https://bugs.openjdk.java.net/browse/JDK-8074839
Webrev: http://cr.openjdk.java.net/~mikael/webrevs/8074839/webrev.03/webrev/

Testing: A slightly earlier version [1] has been through a build & test 
cycle on all the OracleJDK platforms, running the core_tools jtreg tests 
as well as a number of other jtreg tests and java applications. There 
were no warnings on any of the platforms (in the files related to this 
change). I will rerun the testing, but since the differences from the 
earlier version are very small I'd like some reviews first.

Note that the warnings were temporarily disabled as part of JDK-8074096 
[2] until such time they could be fixed the proper way. Also note that 
this change supersedes the earlier change [3] Dmitry had out for review. 
The bug [4] corresponding to that webrev will be closed as a duplicate 
of this bug (JDK-8074839).

Cheers,
Mikael

[1] http://cr.openjdk.java.net/~mikael/webrevs/8074839/webrev.02/webrev
[2] https://bugs.openjdk.java.net/browse/JDK-8074096
[3] http://cr.openjdk.java.net/~dsamersoff/JDK-8073584/webrev.01/
[4] https://bugs.openjdk.java.net/browse/JDK-8073584