Add HW_FAILED error codes for message digest modules

New error codes to report failures from alternative implementations of
MD2, MD4, MD5, RIPEMD160, SHA-1, SHA-256, SHA-512.
diff --git a/library/error.c b/library/error.c
index 151ca4e..9079c5c 100644
--- a/library/error.c
+++ b/library/error.c
@@ -101,6 +101,18 @@
 #include "mbedtls/md.h"
 #endif
 
+#if defined(MBEDTLS_MD2_C)
+#include "mbedtls/md2.h"
+#endif
+
+#if defined(MBEDTLS_MD4_C)
+#include "mbedtls/md4.h"
+#endif
+
+#if defined(MBEDTLS_MD5_C)
+#include "mbedtls/md5.h"
+#endif
+
 #if defined(MBEDTLS_NET_C)
 #include "mbedtls/net_sockets.h"
 #endif
@@ -129,10 +141,26 @@
 #include "mbedtls/pkcs5.h"
 #endif
 
+#if defined(MBEDTLS_RIPEMD160_C)
+#include "mbedtls/ripemd160.h"
+#endif
+
 #if defined(MBEDTLS_RSA_C)
 #include "mbedtls/rsa.h"
 #endif
 
+#if defined(MBEDTLS_SHA1_C)
+#include "mbedtls/sha1.h"
+#endif
+
+#if defined(MBEDTLS_SHA256_C)
+#include "mbedtls/sha256.h"
+#endif
+
+#if defined(MBEDTLS_SHA512_C)
+#include "mbedtls/sha512.h"
+#endif
+
 #if defined(MBEDTLS_SSL_TLS_C)
 #include "mbedtls/ssl.h"
 #endif
@@ -635,6 +663,21 @@
         mbedtls_snprintf( buf, buflen, "HMAC_DRBG - The entropy source failed" );
 #endif /* MBEDTLS_HMAC_DRBG_C */
 
+#if defined(MBEDTLS_MD2_C)
+    if( use_ret == -(MBEDTLS_ERR_MD2_HW_ACCEL_FAILED) )
+        mbedtls_snprintf( buf, buflen, "MD2 - MD2 hardware accelerator failed" );
+#endif /* MBEDTLS_MD2_C */
+
+#if defined(MBEDTLS_MD4_C)
+    if( use_ret == -(MBEDTLS_ERR_MD4_HW_ACCEL_FAILED) )
+        mbedtls_snprintf( buf, buflen, "MD4 - MD4 hardware accelerator failed" );
+#endif /* MBEDTLS_MD4_C */
+
+#if defined(MBEDTLS_MD5_C)
+    if( use_ret == -(MBEDTLS_ERR_MD5_HW_ACCEL_FAILED) )
+        mbedtls_snprintf( buf, buflen, "MD5 - MD5 hardware accelerator failed" );
+#endif /* MBEDTLS_MD5_C */
+
 #if defined(MBEDTLS_NET_C)
     if( use_ret == -(MBEDTLS_ERR_NET_SOCKET_FAILED) )
         mbedtls_snprintf( buf, buflen, "NET - Failed to open a socket" );
@@ -672,6 +715,26 @@
         mbedtls_snprintf( buf, buflen, "PADLOCK - Input data should be aligned" );
 #endif /* MBEDTLS_PADLOCK_C */
 
+#if defined(MBEDTLS_RIPEMD160_C)
+    if( use_ret == -(MBEDTLS_ERR_RIPEMD160_HW_ACCEL_FAILED) )
+        mbedtls_snprintf( buf, buflen, "RIPEMD160 - RIPEMD160 hardware accelerator failed" );
+#endif /* MBEDTLS_RIPEMD160_C */
+
+#if defined(MBEDTLS_SHA1_C)
+    if( use_ret == -(MBEDTLS_ERR_SHA1_HW_ACCEL_FAILED) )
+        mbedtls_snprintf( buf, buflen, "SHA1 - SHA-1 hardware accelerator failed" );
+#endif /* MBEDTLS_SHA1_C */
+
+#if defined(MBEDTLS_SHA256_C)
+    if( use_ret == -(MBEDTLS_ERR_SHA256_HW_ACCEL_FAILED) )
+        mbedtls_snprintf( buf, buflen, "SHA256 - SHA-256 hardware accelerator failed" );
+#endif /* MBEDTLS_SHA256_C */
+
+#if defined(MBEDTLS_SHA512_C)
+    if( use_ret == -(MBEDTLS_ERR_SHA512_HW_ACCEL_FAILED) )
+        mbedtls_snprintf( buf, buflen, "SHA512 - SHA-512 hardware accelerator failed" );
+#endif /* MBEDTLS_SHA512_C */
+
 #if defined(MBEDTLS_THREADING_C)
     if( use_ret == -(MBEDTLS_ERR_THREADING_FEATURE_UNAVAILABLE) )
         mbedtls_snprintf( buf, buflen, "THREADING - The selected feature is not available" );