[Gc] porting Hans Boehm GC to MacOSX

[Andreas Tobler]

>-- Original Message --
>Based on Jeff Sturm's patches, the gc now passes gctest on OS X.  Most
>of the credit goes to him, I just noticed a small bug in his code.  
>
>Things to note:
>
>The changes to linux_threads.c are kind of ugly, with lots of #ifdefs
>to call Mach semaphore_* calls instead of sem_* because sem_init()
>and sem_destroy() always return an error.  If something else would
>be better, introducing GC_sem_* macros, I'll do that instead.
>
>There appears to be no Mach equivalent for sem_getvalue(), so the
>GC_retry_signals code is #ifdefed out.

Not yet applied here.

>Shared libraries are still unsupported, so if you use configure, 
>be sure to pass --disable-shared.  Also, I did not re-run autoconf.  
>
>Here are the patches.  Please review and comment.

Here my first 'real life' feedback.

I applied the version from early this morning (without the retry sig commented)
to the gcc-boehm in gcc-3.3 branch

In the area of libjava I see a failure reduction by at least 6 TC's.

GREAT.
I continue this evening, also I'll apply this patch and test it.

Thank you for work!

Andreas