lang: core: Move template to golang namespace

I don't think this template function should be in any way authoritative,
so let's namespace it.

examples/lang/datetime3.mcl

@@ -1,4 +1,5 @@
 import "datetime"
+import "golang"
 import "sys"
 import "example"
 
@@ -15,5 +16,5 @@ $vumeter = example.vumeter("====", 10, 0.9)
 
 file "/tmp/mgmt/datetime" {
 	state => $const.res.file.state.exists,
-	content => template("Now + 1 year is: {{ .year }} seconds, aka: {{ datetime_print .year }}\n\nload average: {{ .load }}\n\nvu: {{ .vumeter }}\n", $tmplvalues),
+	content => golang.template("Now + 1 year is: {{ .year }} seconds, aka: {{ datetime_print .year }}\n\nload average: {{ .load }}\n\nvu: {{ .vumeter }}\n", $tmplvalues),
 }