make it build with avr32-gcc

Disabled Unix-centric non necessary include files

Changed some include paths

Removed all printf() I put there and there for debugging.

It builds with the avr32 gcc toolchain, meaning we removed
all the pppd code requiring a unix base.

src/netif/ppp/polarssl/des.c

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

src/netif/ppp/polarssl/md4.c

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

src/netif/ppp/polarssl/md5.c

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

src/netif/ppp/polarssl/sha1.c

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