Added SHA3 to MD.

This enables HMAC with SHA3.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>
diff --git a/library/md_wrap.h b/library/md_wrap.h
index 90c7957..50a4093 100644
--- a/library/md_wrap.h
+++ b/library/md_wrap.h
@@ -74,6 +74,12 @@
 #if defined(MBEDTLS_SHA512_C)
 extern const mbedtls_md_info_t mbedtls_sha512_info;
 #endif
+#if defined(MBEDTLS_SHA3_C)
+extern const mbedtls_md_info_t mbedtls_sha3_224_info;
+extern const mbedtls_md_info_t mbedtls_sha3_256_info;
+extern const mbedtls_md_info_t mbedtls_sha3_384_info;
+extern const mbedtls_md_info_t mbedtls_sha3_512_info;
+#endif
 
 #ifdef __cplusplus
 }