RFR(XS): 8154174: improve JitTester performance

[Anton Ivanov]

Hi,
Please review small patch that improves JitTester performance

In current implementation JitTester has exception based logic, which is 
not good by itself, but changing this is quite expensive and there is 
simple way to decrease exception overhead - turn off stack trace in 
ProductionFailedException constructor ( this exception is created very 
often and stack trace is never need, as it only used to control program 
flow )
Also small improvement was done in code that does deep copy of 
SymbolTable element ( Map iteration was rewritten to get rid of multiple 
redundant Map.get() which cost 0(1) only in average case and could be 
worse potentially )

Testing: local

webrev: http://cr.openjdk.java.net/~aaivanov/8154174/webrev
bug: https://bugs.openjdk.java.net/browse/JDK-8154174

-- 
Best regards,
Anton Ivanov