Add some more Lua script examples

scripts/_system_exec.lua

@@ -0,0 +1,20 @@
+ardour { ["type"] = "EditorAction", name = "System Exec" }
+
+function factory () return function ()
+	-- ** EXAMPLES TO RUN EXTERNAL APPLICATIONS ** --
+
+	-- run a command in a shell and wait for it to complete.
+	--
+	-- Details: basically just system(3), except on Unix like systems with
+	-- memory-locking, this call is special-cased to use vfork and close
+	-- file-descriptors. On other systems it defaults to Lua's os-library
+	-- built-in os.execute system() call.
+	os.execute ("date > /tmp/testdate")
+
+	-- os.forkexec() works as fire-and-forget. execv(3) style
+	--
+	-- Details: It calls vfork() and exec() under the hood, passing each
+	-- argument separately to exec (and needs a full-path to the binary).
+	os.forkexec ("/usr/bin/xterm")
+	os.forkexec ("/bin/sh", "-c", "import --frame \"/tmp/scr_$(date).png\"")
+end end