Signup always closes when cron runs, if event module not installed

Evil, yeah. This was introduced by http://drupal.org/node/154580. Oversight on my part that I let this slip past me. :( This is IMHO critical -- we've broken signup.module for sites without event.module, which is a big no-no...

I have a few ideas. Probably the best thing is to replace the series of individual query builder functions for each date-driven feature (reminders and autoclose) with a single function for each one that expects an array. If the function doesn't exist or the array is empty, the feature is disabled. So, for example, in signup_event_5.x-1.inc, instead of this:

function signup_reminder_sql_fields() {
  // We must manually include this here as the event module doesn't
  // include timezone support on all page requests.
  include_once(drupal_get_path('module', 'event') .'/event_timezones.inc');
  return array('e.event_start', 'e.timezone');
}

function signup_reminder_sql_joins() {
  return array('INNER JOIN {event} e ON e.nid = n.nid');
}

function signup_reminder_sql_where() {
  return array('('. time() .' + ((s.reminder_days_before) * 86400)) > e.event_start');
}

We'd have this:

function signup_reminder_sql() {
  // We must manually include this here as the event module doesn't
  // include timezone support on all page requests.
  include_once(drupal_get_path('module', 'event') .'/event_timezones.inc');
  $sql = array();
  $sql['fields'] = array('e.event_start', 'e.timezone');
  $sql['joins'] = array('INNER JOIN {event} e ON e.nid = n.nid');
  $sql['where'] = array('('. time() .' + ((s.reminder_days_before) * 86400)) > \
e.event_start');
  return $sql;
}

Then, in signup_cron(), we'd see if signup_reminder_sql() was defined and returned data. If so, we'd handle the reminder emails, else, we'd skip all of that. Same story with the auto-close SQL and functionality...

This should do it. ;) This patch does the following:

A) Instead of N separate methods for each query fragment for each feature, there are now just 3 SQL query fragment functions that go in the *.inc files:

1. signup_reminder_sql()
2. signup_autoclose_sql()
3. signup_admin_sql()

Each one returns an array of query elements it cares about.

B) Added a _signup_build_query() helper function to merge the results of these backend query element functions with the main, common SQL elements for each feature.

C) Split up signup_cron() into helper functions for each feature.

D) Moved the code to figure out what event-based backend .inc file we need into a method that could be shared by signup_menu() and signup_cron(). Previously, signup_cron() wasn't getting the .inc files at all, since hook_menu() isn't invoked during cron...

E) Added a bunch of phpdoc.

I tested this fairly heavily with event 5.x-1.* enabled and without, for both basic event and story (non-event) nodes, and all the autoclose stuff seems to be working correctly, as is the admin page. I didn't test reminder emails yet (but it's now 5am here and I *really* need sleep).

Reviews and testing would be most appreciated!
Thanks,
-Derek

Works for me with drupal 5.2.
It solves also bug which prevents the cron to run manually from shell.

Committed to HEAD.