Increased the default thread stack limit from 128K to 256K to accomodate

Tracker's custom modules. This may be increased in the future to accomodate
even larger (further nested) scripts.

src/sbbs3/sbbsdefs.h

@@ -69,7 +69,7 @@
 
 #define	JAVASCRIPT_MAX_BYTES		(8*1024*1024)
 #define JAVASCRIPT_CONTEXT_STACK	(16*1024)
-#define JAVASCRIPT_THREAD_STACK		(128*1024)
+#define JAVASCRIPT_THREAD_STACK		(256*1024)
 #define JAVASCRIPT_BRANCH_LIMIT		99999999
 #define JAVASCRIPT_YIELD_INTERVAL	10000
 #define JAVASCRIPT_GC_INTERVAL		100