This fixes an issue where the cipher.h header doesn't compile when included
by C++ code, as C++ is more strict than C about implicit enum casts.

diff -ur polarssl-1.1.1/include/polarssl/cipher.h /home/james/polarssl-1.1.1/include/polarssl/cipher.h
--- polarssl-1.1.1/include/polarssl/cipher.h    2011-11-15 08:38:45.000000000 -0700
+++ /home/james/polarssl-1.1.1/include/polarssl/cipher.h        2012-03-12 17:31:12.279631469 -0600
@@ -313,7 +313,7 @@
 static inline cipher_type_t cipher_get_type( const cipher_context_t *ctx )
 {
     if( NULL == ctx || NULL == ctx->cipher_info )
-        return 0;
+        return POLARSSL_CIPHER_NONE;
 
     return ctx->cipher_info->type;
 }