Add a step for Configure: auto::thread

[fperrad]

Currently PARROT_HAS_THREADS is computed in thread.h and is only accessible from C language.

This patch puts this logic in the step auto::thread, the key HAS_THREADS is added to Config.

Other benefit, an option --without-threads is now available.

[jkeenan]

Replying to fperrad:

François: I commend you on your very thorough preparation of this patch. I appreciate the time and effort you take to get the tests right.

It  passed all tests on Darwin/PPC.

It  passed all tests on Linux/i386.

The extent to which the tests cover the code can be seen  here.

Two small points, then two larger questions:

1. t/steps/auto_thread-01.t Line 20: s/crypto/threads/

2. We will need to update MANIFEST before applying: perl tools/dev/mk_manifest_and_skip.pl

Larger questions:

3. Is there any way this patch could be done as part of an already existing configuration step?

Personally, I like it the way it is and I wouldn't want to muddy up some other step just to save a few processes. But I can bet that other contributors will raise that question, so I'm anticipating them.

4. While I'm satisfied with this addition, I'm no expert in threads. Does anyone else care to comment?

Thank you very much.

kid51

[fperrad]

fix --without-threads on linux

[jkeenan]

I re-tested with step-thread-v2.patch.

make test passed on Darwin/PPC.

make fulltest passed on Linux/i386.

Okay by me to apply to trunk.

kid51

[fperrad]

Applied in r39976