Move declaration of struct ip4_addr_packed and ip4_addr_p_t to prot/ip4.h

The types are used in structs declared in ip4.h.

src/include/lwip/ip4_addr.h

@@ -52,24 +52,9 @@ struct ip4_addr {
   u32_t addr;
 };
 
-/** This is the packed version of ip4_addr_t,
-   used in network headers that are itself packed */
-#ifdef PACK_STRUCT_USE_INCLUDES
-#  include "arch/bpstruct.h"
-#endif
-PACK_STRUCT_BEGIN
-struct ip4_addr_packed {
-  PACK_STRUCT_FIELD(u32_t addr);
-} PACK_STRUCT_STRUCT;
-PACK_STRUCT_END
-#ifdef PACK_STRUCT_USE_INCLUDES
-#  include "arch/epstruct.h"
-#endif
-
 /** ip4_addr_t uses a struct for convenience only, so that the same defines can
  * operate both on ip4_addr_t as well as on ip4_addr_p_t. */
 typedef struct ip4_addr ip4_addr_t;
-typedef struct ip4_addr_packed ip4_addr_p_t;
 
 /**
  * struct ipaddr2 is used in the definition of the ARP packet format in

src/include/lwip/prot/ip4.h

@@ -44,6 +44,22 @@
 extern "C" {
 #endif
 
+/** This is the packed version of ip4_addr_t,
+    used in network headers that are itself packed */
+#ifdef PACK_STRUCT_USE_INCLUDES
+#  include "arch/bpstruct.h"
+#endif
+PACK_STRUCT_BEGIN
+struct ip4_addr_packed {
+  PACK_STRUCT_FIELD(u32_t addr);
+} PACK_STRUCT_STRUCT;
+PACK_STRUCT_END
+#ifdef PACK_STRUCT_USE_INCLUDES
+#  include "arch/epstruct.h"
+#endif
+
+typedef struct ip4_addr_packed ip4_addr_p_t;
+
 /* Size of the IPv4 header. Same as 'sizeof(struct ip_hdr)'. */
 #define IP_HLEN 20