[slime-devel] SBCL - slime-restore support (take 2)

Hello SLIME developers,

More elaborate patch for SBCL snapshot support is attached. * Fixed alien array initialization for execve (and execv is now used); * Added posix error handling for execv; * Use *runtime-pathname*'s namestring to find executable reliably; * I/O redirection is now restored correctly with (create-repl).

Unfortunately, there are some parts that I just can't get right, e.g. fd-handlers accumulating in sb-impl::*descriptor-handlers* (for now, I simply #+sbcl (remove them on startup)), file descriptor of the old core that is inherited (now I turn on FD_CLOEXEC on fd#3, that is normally the old core).

However, with all this "duct tape", it works.