RFR 8139875: [TESTBUG] Improve nsk/stress/stack/* tests

[Harold Seigel]

Hi,

Please review these small changes to reduce the amount of time required 
by some of the nsk/stress/stack tests in order to prevent them from 
timing out.  The changes include using -Xss to run the tests with 
smaller stacks, prevent running with -Xcomp, and, for test stack019, 
reduce the number of test iterations.

Test stack019 was excluded from windows targets because, even with the 
reduced iterations, the test was running for > 48 minutes.

Open Webrev: 
http://cr.openjdk.java.net/~hseigel/bug_8139875/webrev/index.html

JBS Bug: https://bugs.openjdk.java.net/browse/JDK-8139875

The tests were tested by running them in Mach5 tier5 and tier7 and 
looking at their execution time.

Thanks, Harold