Checking in three Darwin-specific patches.

Tony Lownds: [ Patch #101816 ] Fixes shared modules on Mac OS X

    1. Mac OS X is recognized by the Next-ish host recognition code as
    "Darwin/1.2"

    2. When specifying just --with-dyld, modules can compile as shared

    3. --with-dyld and --with-next-framework, modules can compile as
    shared

    4. --with-suffix=.exe, and Lib/plat-darwin1.2 is being made, the regen
    script invokes python as python.exe

    [I had to reformat this patch a bit to make it work.  Please test!]

Dan Wolfe: [ Patch #101823 ] Fix Darwin POSIX Thread redefinition

    The patch below fixes the redefinition problem in Darwin with
    _POSIX_THREADS. I'm not sure if this is the correct long term fix but
    for now it fixes the problem and the fix is specific to Darwin.

Dan Wolfe: [ Patch #101824 ] On Darwin, remove unrecognized option
                             `-OPT:Olimit=0'

  After many, many, many compiles, I finally got itchy of this warning
  cluttering up the output... so I scratched (Darwin configs only) and
  it's gone! :-)

configure.in

@@ -341,7 +341,10 @@ AC_TRY_RUN([int main() { return 0; }],
 CC="$ac_save_cc"])
 AC_MSG_RESULT($ac_cv_opt_olimit_ok)
 if test $ac_cv_opt_olimit_ok = yes; then
-  OPT="$OPT -OPT:Olimit=0"
+    case $ac_sys_system in
+      Darwin*) OPT="$OPT" ;;
+      *) OPT="$OPT -OPT:Olimit=0";;
+    esac
 else
   AC_MSG_CHECKING(whether $CC accepts -Olimit 1500)
   AC_CACHE_VAL(ac_cv_olimit_ok,
@@ -493,6 +496,9 @@ fi
 # Minor variations in building a framework between NextStep versions 4 and 5
 AC_SUBST(LIBTOOL_CRUFT)
 case $ac_sys_system/$ac_sys_release in
+  Darwin/*)
+    ns_undef_sym='_environ'
+    LIBTOOL_CRUFT="-lcc_dynamic -arch_only ppc -U $ns_undef_sym" ;;
   next/4*)
     ns_undef_sym='__environ'
     LIBTOOL_CRUFT="-U $ns_undef_sym" ;;
@@ -568,7 +574,11 @@ then
 	DYNIX/ptx*) LDSHARED="ld -G";;
         Darwin/*|next/*) 
 		if test "$ns_dyld"
-		then LDSHARED='$(CC) $(LDFLAGS) -bundle -prebind'
+		then 
+		  if test "$ac_sys_system" = Darwin
+		  then LDSHARED='$(CC) $(LDFLAGS) -bundle -undefined suppress'
+		  else LDSHARED='$(CC) $(LDFLAGS) -bundle -prebind'
+		  fi
 		else LDSHARED='$(CC) $(CFLAGS) -nostdlib -r';
 		fi
 	if test "$with_next_framework" ; then
@@ -639,6 +649,7 @@ then
 	# crt1.o) gets erroneously defined as common, which breaks dynamic
 	# loading of any modules which reference it in System.framework
 	next/4*|next/5*) LINKFORSHARED="-u __dummy -framework System" ;;
+	Darwin/*) LINKFORSHARED="-framework System" ;;
 	SCO_SV*) LINKFORSHARED="-Bdynamic -dy -Wl,-Bexport";;
 	ReliantUNIX*) LINKFORSHARED="-W1 -Blargedynsym";;
 	FreeBSD*|NetBSD*) 
@@ -761,7 +772,10 @@ else
     LIBS="-lpthread $LIBS"
     LIBOBJS="$LIBOBJS thread.o"],[
     AC_CHECK_FUNC(pthread_detach, [AC_DEFINE(WITH_THREAD)
-    AC_DEFINE(_POSIX_THREADS)
+    case $ac_sys_system in
+      Darwin*) ;;
+      *) AC_DEFINE(_POSIX_THREADS);;
+    esac
     LIBOBJS="$LIBOBJS thread.o"],[
     AC_CHECK_HEADER(kernel/OS.h, [AC_DEFINE(WITH_THREAD)
     AC_DEFINE(BEOS_THREADS)
@@ -911,7 +925,7 @@ then
 	AIX*) DYNLOADFILE="dynload_aix.o";;
 	BeOS*) DYNLOADFILE="dynload_beos.o";;
 	hp*|HP*) DYNLOADFILE="dynload_hpux.o";;
-	next/*) DYNLOADFILE="dynload_next.o";;
+	Darwin/*|next/*) DYNLOADFILE="dynload_next.o";;
 	*)
 	# use dynload_shlib.c and dlopen() if we have it; otherwise stub
 	# out any dynamic loading