Implement the System#sleep function

fixes #12411

doc/19-library-reference.md

@@ -26,6 +26,7 @@ escape\_shell\_arg(text)        | Escapes a string for use as a single shell arg
 escape\_shell\_cmd(text)        | Escapes shell meta characters in a string.
 escape\_create\_process\_arg(text)| (Windows only) Escapes a string for use as an argument for CreateProcess().
 exit(integer)                   | Terminates the application.
+sleep(interval)                 | Sleeps for the specified amount of time (in seconds).
 
 ## <a id="object-accessor-functions"></a> Object Accessor Functions
 

lib/base/scriptutils.cpp

@@ -66,6 +66,7 @@ REGISTER_SAFE_SCRIPTFUNCTION_NS(System, escape_shell_arg, &Utility::EscapeShellA
 REGISTER_SAFE_SCRIPTFUNCTION_NS(System, escape_create_process_arg, &Utility::EscapeCreateProcessArg);
 #endif /* _WIN32 */
 REGISTER_SCRIPTFUNCTION_NS(System, ptr, &ScriptUtils::Ptr);
+REGISTER_SCRIPTFUNCTION_NS(System, sleep, &Utility::Sleep);
 
 String ScriptUtils::CastString(const Value& value)
 {