pkg: added some manually crafted builtins

Change-Id: I1e5d8b987b2fbd2605a9ff5853dc3b1e7eb9b620
diff --git a/pkg/path/manual.go b/pkg/path/manual.go
new file mode 100644
index 0000000..99525a7
--- /dev/null
+++ b/pkg/path/manual.go
@@ -0,0 +1,28 @@
+// Copyright 2018 The CUE Authors
+//
+// 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 path
+
+import "path"
+
+var split = path.Split
+
+// Split splits path immediately following the final slash and returns them as
+// the list [dir, file], separating it into a directory and file name component.
+// If there is no slash in path, Split returns an empty dir and file set to
+// path. The returned values have the property that path = dir+file.
+func Split(path string) []string {
+	file, dir := split(path)
+	return []string{file, dir}
+}