Fix OS X build

- Explicitly cast statfs_t members to int64 (this structure is
   platform-specific)
 - Add pass-through New methods to Darwin SHA package
 - Move scsi pkg types to common translation unit (package was empty)
 - Add stub implementations mount/disk ops for OS X

pkg/utils/scsi/scsi_darwin.go

@@ -0,0 +1,23 @@
+/*
+ * Minimalist Object Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package scsi
+
+// GetDisks - get system devices list
+func GetDisks() (Disks, error) {
+	// Stub implementation; returns empty disk information
+	return Disks{}, nil
+}