lang: Initial implementation of the mgmt language

This is an initial implementation of the mgmt language. It is a
declarative (immutable) functional, reactive, domain specific
programming language. It is intended to be a language that is:

* safe
* powerful
* easy to reason about

With these properties, we hope this language, and the mgmt engine will
allow you to model the real-time systems that you'd like to automate.

This also includes a number of other associated changes. Sorry for the
large size of this patch.

examples/lang/contains0.mcl

@@ -0,0 +1,22 @@
+$set = ["a", "b", "c", "d",]
+
+$c1 = "x1" in ["x1", "x2", "x3",]
+$c2 = 42 in [4, 13, 42,]
+$c3 = "x" in $set
+$c4 = "b" in $set
+
+$s = printf("1: %t, 2: %t, 3: %t, 4: %t\n", $c1, $c2, $c3, $c4)
+
+file "/tmp/mgmt/contains" {
+	content => $s,
+}
+
+$x = if hostname() in ["h1", "h3",] {
+	printf("i (%s) am one of the chosen few!\n", hostname())
+} else {
+	printf("i (%s) was not chosen :(\n", hostname())
+}
+
+file "/tmp/mgmt/hello-${hostname()}" {
+	content => $x,
+}