prevent conflict with existing (md4|md5|sha1|des) object file if polarssl is already used elsewhere in the project

src/netif/ppp/polarssl/lwip_des.c

@@ -42,7 +42,7 @@
 #include "lwip/opt.h"
 #if LWIP_INCLUDED_POLARSSL_DES
 
-#include "des.h"
+#include "lwip_des.h"
 
 /*
  * 32-bit integer manipulation macros (big endian)

src/netif/ppp/polarssl/lwip_md4.c

@@ -42,7 +42,7 @@
 #include "lwip/opt.h"
 #if LWIP_INCLUDED_POLARSSL_MD4
 
-#include "md4.h"
+#include "lwip_md4.h"
 
 /*
  * 32-bit integer manipulation macros (little endian)

src/netif/ppp/polarssl/lwip_md5.c

@@ -41,7 +41,7 @@
 #include "lwip/opt.h"
 #if LWIP_INCLUDED_POLARSSL_MD5
 
-#include "md5.h"
+#include "lwip_md5.h"
 
 /*
  * 32-bit integer manipulation macros (little endian)

src/netif/ppp/polarssl/lwip_sha1.c

@@ -41,7 +41,7 @@
 #include "lwip/opt.h"
 #if LWIP_INCLUDED_POLARSSL_SHA1
 
-#include "sha1.h"
+#include "lwip_sha1.h"
 
 /*
  * 32-bit integer manipulation macros (big endian)