Add HTTP/TLS obfuscating. [SIP001] (#1009)

Add experimental HTTP/TLS obfuscating as an **optional extension** of shadowsocks protocol.

More discussions can be found here: https://github.com/shadowsocks/shadowsocks-org/issues/26

As this feature is still a SIP (Shadowsocks Improvement Proposal), it's very unstable and experimental. So, 

1. Don't enable it unless you know what it is.
2. Be very careful when using it in production environment.

src/utils.h

@@ -229,4 +229,27 @@ void *ss_realloc(void *ptr, size_t new_size);
         ptr = NULL;      \
     } while (0)
 
+#if BYTE_ORDER == BIG_ENDIAN
+
+#define CT_HTONS(n) (n)
+#define CT_NTOHS(n) (n)
+#define CT_HTONL(n) (n)
+#define CT_NTOHL(n) (n)
+
+#else
+
+#define CT_HTONS(n) (((((unsigned short)(n) & 0xFF)) << 8) | (((unsigned short)(n) & 0xFF00) >> 8))
+#define CT_NTOHS(n) (((((unsigned short)(n) & 0xFF)) << 8) | (((unsigned short)(n) & 0xFF00) >> 8))
+
+#define CT_HTONL(n) (((((unsigned long)(n) & 0xFF)) << 24) | \
+                          ((((unsigned long)(n) & 0xFF00)) << 8) | \
+                          ((((unsigned long)(n) & 0xFF0000)) >> 8) | \
+                          ((((unsigned long)(n) & 0xFF000000)) >> 24))
+
+#define CT_NTOHL(n) (((((unsigned long)(n) & 0xFF)) << 24) | \
+                          ((((unsigned long)(n) & 0xFF00)) << 8) | \
+                          ((((unsigned long)(n) & 0xFF0000)) >> 8) | \
+                          ((((unsigned long)(n) & 0xFF000000)) >> 24))
+#endif
+
 #endif // _UTILS_H