pkg: hide it by moving to _pkg.dev

The idea here is to preserve the history of `dev` branch development and its
code when merging with the `master`. Later this code could be moved into the
masters code where appropriate.

_pkg.dev/wire/util/slice/slice.go

@@ -0,0 +1,15 @@
+package slice
+
+// Reverse return a reversed version of the given byte slice.
+func Reverse(b []byte) []byte {
+	// Protect from big.Ints that have 1 len bytes.
+	if len(b) < 2 {
+		return b
+	}
+
+	dest := make([]byte, len(b))
+	for i, j := 0, len(b)-1; i < j+1; i, j = i+1, j-1 {
+		dest[i], dest[j] = b[j], b[i]
+	}
+	return dest
+}