listObjects: do not do stat during readdir()

* listObjects: improve response time by not doing stat during readDir() operation.

* listObjects: Add windows support.

* listObjects: Readdir() in batches to conserve memory. Add solaris build.

* listObjects: cleanup code.

fs-object.go

@@ -33,6 +33,23 @@ import (
 	"github.com/minio/minio/pkg/probe"
 )
 
+// isDirEmpty - returns whether given directory is empty or not.
+func isDirEmpty(dirname string) (status bool, err error) {
+	f, err := os.Open(dirname)
+	if err == nil {
+		defer f.Close()
+		if _, err = f.Readdirnames(1); err == io.EOF {
+			status = true
+			err = nil
+
+		}
+
+	}
+
+	return
+
+}
+
 /// Object Operations
 
 // GetObject - GET object