RFR(S): 8233193: Incorrect bailout from possibly_add_compiler_threads

[Doerr, Martin]

Hi,

I'd like to cleanup exception handling in CompileBroker a little bit.

Here's my proposal:
- Use THREAD instead of CHECK where no exceptions get thrown.
- Remove unused preload_classes.
- make_thread: Rename thread to new_thread to avoid confusion with THREAD (the current compiler thread).
- possibly_add_compiler_threads: Remove usage of EXCEPTION_MARK + CHECK because this functions is not supposed to kill the VM on exceptions. Add assertion to caller.

Webrev:
http://cr.openjdk.java.net/~mdoerr/8233193_CompileBroker/webrev.00/

@David:
You didn't like usage of the CHECK macro in the initialization functions, but I think they are ok.
Not very nice to read, but the behavior looks ok to me.
At least, I didn't find a better replacement for them. Maybe you have a proposal?

Best regards,
Martin