build: Add release builds, now generated with 'make release'

Currently supported platforms are

    - linux{amd64,arm,386}
    - winows{amd64,386}
    - darwin{amd64}

buildscripts/gen-ldflags.go

@@ -37,7 +37,7 @@ func genLDFlags(version string) string {
 
 // genReleaseTag prints release tag to the console for easy git tagging.
 func releaseTag(version string) string {
-	relPrefix := "UNOFFICIAL"
+	relPrefix := "DEVELOPMENT"
 	if prefix := os.Getenv("MINIO_RELEASE"); prefix != "" {
 		relPrefix = prefix
 	}