Add Poly1305 authenticator algorithm (RFC 7539)

Test vectors are included from RFC 7539.

Poly1305 is also added to the benchmark program.
diff --git a/programs/test/benchmark.c b/programs/test/benchmark.c
index bc473cf..c419665 100644
--- a/programs/test/benchmark.c
+++ b/programs/test/benchmark.c
@@ -63,6 +63,7 @@
 #include "mbedtls/gcm.h"
 #include "mbedtls/ccm.h"
 #include "mbedtls/cmac.h"
+#include "mbedtls/poly1305.h"
 #include "mbedtls/havege.h"
 #include "mbedtls/ctr_drbg.h"
 #include "mbedtls/hmac_drbg.h"
@@ -95,7 +96,8 @@
 #define OPTIONS                                                         \
     "md4, md5, ripemd160, sha1, sha256, sha512,\n"                      \
     "arc4, des3, des, camellia, blowfish, chacha20,\n"                  \
-    "aes_cbc, aes_gcm, aes_ccm, aes_cmac, des3_cmac,\n"                 \
+    "aes_cbc, aes_gcm, aes_ccm,\n"                                      \
+    "aes_cmac, des3_cmac, poly1305\n"                                   \
     "havege, ctr_drbg, hmac_drbg\n"                                     \
     "rsa, dhm, ecdsa, ecdh.\n"
 
@@ -231,6 +233,7 @@
          arc4, des3, des,
          aes_cbc, aes_gcm, aes_ccm, aes_cmac, des3_cmac,
          camellia, blowfish, chacha20,
+         poly1305,
          havege, ctr_drbg, hmac_drbg,
          rsa, dhm, ecdsa, ecdh;
 } todo_list;
@@ -289,6 +292,8 @@
                 todo.blowfish = 1;
             else if( strcmp( argv[i], "chacha20" ) == 0 )
                 todo.chacha20 = 1;
+            else if( strcmp( argv[i], "poly1305" ) == 0 )
+                todo.poly1305 = 1;
             else if( strcmp( argv[i], "havege" ) == 0 )
                 todo.havege = 1;
             else if( strcmp( argv[i], "ctr_drbg" ) == 0 )
@@ -530,6 +535,13 @@
     }
 #endif
 
+#if defined(MBEDTLS_POLY1305_C)
+    if ( todo.poly1305 )
+    {
+        TIME_AND_TSC( "Poly1305", mbedtls_poly1305_mac( buf, BUFSIZE, buf, buf ) );
+    }
+#endif
+
 #if defined(MBEDTLS_BLOWFISH_C) && defined(MBEDTLS_CIPHER_MODE_CBC)
     if( todo.blowfish )
     {