RFR: 8133561: linux thread id should be reported in decimal in the error reports now

[Rachel Protacio]

Hello, everyone! I've just started with the Hotspot Runtime team - 
please take a look at this change.
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Summary: Linux thread id error reports changed back to decimal

Bug: https://bugs.openjdk.java.net/browse/JDK-8133561
Webrev: http://cr.openjdk.java.net/~coleenp/8133561/

Testing: I visually verified the result with error logs and Show 
MessageBoxOnError. Passed jtreg hotspot/test/runtime and RBT "quick" tests.

Thank you!
Rachel