RFR (S): 8010913 : compiler/6863420 often exceeds timeout

[David Chase]

Problem:
The test runs over-long on some test machines, causing timeouts and spurious failures
if JPRT is used to check compiler tests across a range of machines.
A four-minute run was observed in one case.

Fix:
Add an increased timeout and a timeout thread for shutting down the test early.

Testing:
JPRT of that test across all available platforms with an artificially short timeout
to ensure that the timeout thread worked as expected, manual check of successful
runs to be sure that the timeout thread did its job (i.e., saw runs for a hair more than
the time limit, as well as short runs).

webrev:
http://cr.openjdk.java.net/~drchase/8010913/webrev.00/