[build] add --enable-dev-tools configure flag

This builds tools that I want to keep in the same code base, but not
intended for general release.

thin-provisioning/thin_generate_metadata.cc

@@ -0,0 +1,25 @@
+#include "thin-provisioning/commands.h"
+
+using namespace thin_provisioning;
+
+//----------------------------------------------------------------
+
+thin_generate_metadata_cmd::thin_generate_metadata_cmd()
+	: command("thin_generate_metadata")
+{
+}
+
+void
+thin_generate_metadata_cmd::usage(std::ostream &out) const
+{
+
+}
+
+int
+thin_generate_metadata_cmd::run(int argc, char **argv)
+{
+
+	return 1;
+}
+
+//----------------------------------------------------------------