make debugger thread invisible

src/debugger.c

@@ -58,6 +58,7 @@ static void hl_debug_loop( hl_module *m ) {
 	flags |= 4;
 	loop = true;
 #	endif
+	hl_get_thread()->exc_flags |= HL_THREAD_INVISIBLE;
 	do {
 		int i;
 		vbyte cmd;

src/hl.h

@@ -807,6 +807,7 @@ struct _hl_trap_ctx {
 #define HL_EXC_CATCH_ALL	2
 #define HL_EXC_IS_THROW		4
 #define HL_TRACK_DISABLE	8
+#define HL_THREAD_INVISIBLE	16
 
 typedef struct {
 	int thread_id;