increase websocket stack size to give leeway to increase the size of the biobuf buffer

Reference: /n/atom/patch/applied/websocketstk
Date: Fri Apr 18 00:02:57 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/ip/httpd/websocket.c	Fri Apr 18 00:02:57 2014
+++ /sys/src/cmd/ip/httpd/websocket.c	Fri Apr 18 00:02:57 2014
@@ -54,8 +54,8 @@
 	int type;
 };
 
-/* XXX The default was not enough, but this is just a guess. */
-int mainstacksize = 65536;
+/* XXX The default was not enough, but this is just a guess. at least 2*sizeof Biobuf */
+int mainstacksize = 128*1024;
 
 const char wsnoncekey[] = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 const char wsversion[] = "13";