put LWIP_MAX and LWIP_MIN macros in def.h and use these instead of locally declaring them in .c files

src/core/tcp.c

@@ -70,8 +70,6 @@ struct tcp_pcb *tcp_tw_pcbs;      /* List of all TCP PCBs in TIME-WAIT. */
 
 struct tcp_pcb *tcp_tmp_pcb;
 
-#define LWIP_MIN(x,y) (x) < (y)? (x): (y)
-
 static u8_t tcp_timer;
 
 static u16_t tcp_new_port(void);

src/core/tcp_in.c

@@ -654,7 +654,7 @@ tcp_receive(struct tcp_pcb *pcb)
 				  ntohl(pcb->unacked->tcphdr->seqno)));
 	    tcp_rexmit(pcb);
 	    /* Set ssthresh to max (FlightSize / 2, 2*SMSS) */
-	    pcb->ssthresh = UMAX((pcb->snd_max -
+	    pcb->ssthresh = LWIP_MAX((pcb->snd_max -
 				  pcb->lastack) / 2,
 				 2 * pcb->mss);
 	    

src/core/tcp_out.c

@@ -59,9 +59,6 @@
 #include "lwip/stats.h"
 
 #if LWIP_TCP
-#define LWIP_MIN(x,y) (x) < (y)? (x): (y)
-
-
 
 /* Forward declarations.*/
 static void tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb);