Make forkProcess work with +RTS -N

Consider this experimental for the time being.  There are a lot of
things that could go wrong, but I've verified that at least it works
on the test cases we have.

I also did some API cleanups while I was here.  Previously we had:

Capability * rts_eval (Capability *cap, HaskellObj p, /*out*/HaskellObj *ret);

but this API is particularly error-prone: if you forget to discard the
Capability * you passed in and use the return value instead, then
you're in for subtle bugs with +RTS -N later on.  So I changed all
these functions to this form:

void rts_eval (/* inout */ Capability **cap,
               /* in    */ HaskellObj p,
               /* out */   HaskellObj *ret)

It's much harder to use this version incorrectly, because you have to
pass the Capability in by reference.

1 files changed, 1 insertions, 1 deletions

diff --git a/rts/Stable.c b/rts/Stable.c
index c46f8b2b9e..39b26173d8 100644
--- a/rts/Stable.c
+++ b/rts/Stable.c
@@ -77,7 +77,7 @@ static snEntry *stable_ptr_free = NULL;
 static unsigned int SPT_size = 0;
 
 #ifdef THREADED_RTS
-static Mutex stable_mutex;
+Mutex stable_mutex;
 #endif
 
 static void enlargeStablePtrTable(void);