Codereview needed for #6929479

[Xueming Shen]

http://cr.openjdk.java.net/~sherman/6929479/webrev/

This is a rfe to add a system property sun.zip.disableMmap to enable the 
end user to disable the mmap usage in
Sun's java.util.zip.ZipFile implementaiton (for Solaris and Linux 
platforms).

Application uses java.util.zip.ZipFile might experience SIGBUS vm crash 
if the application mistakely over-writes
zip/jar files that are still being used, for example the application 
server repeatedly deploy the same jar file into the
same location again and again while there is still code (running in the 
same vm)  still accessing this particular zip/
jar file (access the memory that mmapped the central directory of the 
zip file). While this is indeed an programming
error in the offending application, there is situation that the end user 
really does not have the control of those
applications and look for a workaround for the crash. With this property 
set to true (-Dsun.zip.disableMmap=true)
the sun zipfile implementation reads in the central directory into the 
memory instead of using mmap.

Thanks,
Sherman