Improve AJAX support for info windows (marker bubbles)

This patch improves support of remote AJAX callbacks for info windows (marker popups).

rmtcallback property is now optional, so that absolute uris from different domains can be handled in the same marker set by setting the full uri in marker.rmt.

Since getting the info window content is an http request that can take time to be responded to, a loading image (spinning circle) has been added and displays while the http request is being made. If marker.text is set then that is used instead of the loading image.

This patch includes diff lines from patches at http://drupal.org/node/238471 and http://drupal.org/node/236029 and will need to be re-rolled once they are committed.

The parts that are new in this patch are:

   $mms = variable_get('gmap_markermanager', array());
   if (empty($mms[$mm])) {
     $mms[$mm] = array();
   }
+
+  // Html markup for the spinning 'loading' image for asynchronous callbacks
+  drupal_add_js(array('loadingImage' => theme('gmap_loading_image')), 'setting');
   drupal_add_js(array('gmap_markermanager' => $mms[$mm]), 'setting');
-// @@@
-drupal_add_js($gmap_path .'/js/poly.js');
+  drupal_add_js($gmap_path .'/js/poly.js', 'module', 'header', null, null, false);
   $key = variable_get('googlemap_api_key', '');
   if (module_exists('keys_api')) {
     $key = keys_api_get_key('gmap', $_SERVER['HTTP_HOST']);
@@ -185,6 +214,12 @@ drupal_add_js($gmap_path .'/js/poly.js')
   $gmap_initialized = TRUE;
 }
 
+function theme_gmap_loading_image() {
+  $t = t('Loading...');
+  $att = array('class' => 'gmap-loading-image');
+  return theme('image', drupal_get_path('module', 'gmap') .'/loading.gif', $t, $t, $att);
+}
+
 /**
  * Cleans the gmap variables to prevent javascript interjection.
  *