fixes of OpenSolaris

Make the GC always use the mmap() block cache, since mmap() on Solaris
allocates much more than a page when a single page is requested.

Enable places and threads by default on x86 and x86_64.

Fix pthread-related compilation flags.
fix subprocess issues

Fix SIGCHLD suspension for fork()-based file locks (i.e., Solaris).

Also, fix commit ea51d32e, which broke termination of process groups
where the main process terminated before the rest of the group,
because it used sigwait() before the terminate action.