Allow ksh to compile on Haiku; implement SIGKILLTHR support (#408)

This commit implements the build fixes required to get ksh running on
Haiku. Note that while ksh does compile, it has a ton of regression test
failures on Haiku.

src/cmd/ksh93/data/signals.c,
src/lib/libast/features/signal.c:
- Add support for the SIGKILLTHR signal, which is supported by BeOS and
  Haiku.
- SIGINFO was missing an entry in the libast feature test, so add one
  (re: 658bba74).

src/cmd/ksh93/RELEASE:
- Add an entry noting that ksh now compiles on Haiku, albeit with many
  regression test failures.

src/cmd/ksh93/{include/terminal.h,sh/path.c}:
- Silence compiler warnings on Haiku.

src/lib/libast/features/mmap:
- The mmap feature test freezes on Haiku, so modify the test to fail
  immediately on that OS.

src/lib/libast/misc/signal.c:
- Avoid redefining the signal definition on Haiku to fix a compiler
  error.

src/lib/libast/features/nl_types:
- For some reason the nl_item typedef on Haiku doesn't work correctly.
  Work around that by creating the nl_item type in the libast nl_types
  feature test.

src/lib/libast/features/mmap

@@ -19,6 +19,9 @@ tst	lib_mmap note{ standard mmap interface that works }end execute{
 	int
 	main(int argc, char** argv)
 	{
+	#ifdef __HAIKU__
+		return 1;  /* don't even bother, on Haiku it freezes the system */
+	#endif
 		caddr_t		mm;
 		char		*t, *u, *f;
 		int		i, fd, okfixed;

src/lib/libast/features/nl_types

@@ -19,6 +19,9 @@ tst	output{
 		printf("#include <%s>	/* the native nl_types.h */\n", _nxt_nl_types_str);
 	#endif
 		printf("\n");
+		printf("#ifdef __HAIKU__\n");
+		printf("typedef int	nl_item;  /* workaround system header bug */\n");
+		printf("#endif\n");
 	#ifndef NL_SETMAX
 		printf("#undef	NL_SETMAX\n");
 		printf("#define NL_SETMAX	1023\n");

src/lib/libast/features/signal.c

@@ -120,6 +120,10 @@ static struct _m_ map[] =
 #define HAD_SIGILL	1
 "Illegal instruction",		"ILL",		SIGILL,
 #endif
+#ifdef SIGINFO
+#define HAD_SIGINFO	1
+"Information request", 		"INFO",		SIGINFO,
+#endif
 #ifdef SIGINT
 #define HAD_SIGINT	1
 "Interrupt",			"INT",		SIGINT,
@@ -136,6 +140,10 @@ static struct _m_ map[] =
 #define HAD_SIGKILL	1
 "Killed",			"KILL",		SIGKILL,
 #endif
+#ifdef SIGKILLTHR
+#define HAD_SIGKILLTHR	1
+"Kill Thread",			"KILLTHR",	SIGKILLTHR,
+#endif
 #ifdef SIGLAB
 #define HAD_SIGLAB	1
 "Security label changed",	"LAB",		SIGLAB,

src/lib/libast/misc/signal.c

@@ -26,7 +26,7 @@
  * fun==SIG_DFL also unblocks signal
  */
 
-#if !_UWIN
+#if !_UWIN && !__HAIKU__
 
 #undef	signal
 #define signal		______signal