Code Review 6863419: MimeTable initialization is too greedy

[Chris Hegarty]

Alan, Michael,

This is the JDK part of the changes for this CR. Trivially, it just 
fixes the unsafe lazy initialization of default instance of MimeTable.

http://cr.openjdk.java.net/~chegar/6863419/webrev.00/webrev/

Thanks,
-Chris.