Fix some dependencies/warnings in programs
diff --git a/programs/pkey/pk_decrypt.c b/programs/pkey/pk_decrypt.c
index 416bbec..8e0d9aa 100644
--- a/programs/pkey/pk_decrypt.c
+++ b/programs/pkey/pk_decrypt.c
@@ -97,9 +97,7 @@
 
     if( ( ret = pk_parse_keyfile( &pk, argv[1], "" ) ) != 0 )
     {
-        polarssl_strerror( ret, (char *) buf, sizeof(buf) );
-        printf( " failed\n  ! pk_parse_keyfile returned -0x%04x - %s\n\n", -ret,
-                buf );
+        printf( " failed\n  ! pk_parse_keyfile returned -0x%04x\n", -ret );
         goto exit;
     }
 
@@ -131,9 +129,7 @@
     if( ( ret = pk_decrypt( &pk, buf, i, result, &olen, sizeof(result),
                             ctr_drbg_random, &ctr_drbg ) ) != 0 )
     {
-        polarssl_strerror( ret, (char *) buf, sizeof(buf) );
-        printf( " failed\n  ! pk_decrypt returned -0x%04x - %s\n\n", -ret,
-                buf );
+        printf( " failed\n  ! pk_decrypt returned -0x%04x\n", -ret );
         goto exit;
     }
 
@@ -145,6 +141,11 @@
 
 exit:
 
+#if defined(POLARSSL_ERROR_C)
+    polarssl_strerror( ret, (char *) buf, sizeof(buf) );
+    printf( "  !  Last error was: %s\n", buf );
+#endif
+
 #if defined(_WIN32)
     printf( "  + Press Enter to exit this program.\n" );
     fflush( stdout ); getchar();