RFR JDK-8042888: Remove extcheck tool

[Pavel Rappo]

Hi everyone,

Could you please review my change for JDK-8042888?

http://cr.openjdk.java.net/~prappo/8042888/webrev.00/

Previously I sent an email to see if anyone uses this tool or has any thoughts on its future [1].

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[1] http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-September/028648.html

Thanks
-Pavel