Added RT_LWIP_PBUF_POOL_BUFSIZE to handle PBUF_POOL_BUFSIZE definition in user configuration file.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2072 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/net/lwip/src/lwipopts.h

@@ -139,7 +139,9 @@
 #endif
 
 /* PBUF_POOL_BUFSIZE: the size of each pbuf in the pbuf pool. */
-#define PBUF_POOL_BUFSIZE           1500
+#ifdef RT_LWIP_PBUF_POOL_BUFSIZE
+#define PBUF_POOL_BUFSIZE			 RT_LWIP_PBUF_POOL_BUFSIZE
+#endif
 
 /* PBUF_LINK_HLEN: the number of bytes that should be allocated for a
    link level header. */