Introduce a hook_variables and make variable_get() only one parameter

Hi.

So, funny story. Month or two ago, I was searching web with google, but it very slow. So I do some research, and I find Google powered by Drupal. And Drupal open source, so I figure out what wrong!

So I set Drupal local, and I see what make it slow. But I get distracted! I see variable_get calls all over, everywhere. But there are two parameters! I do not like this. So I set up new hook_variables() that work well for this.

With this patch, Drupal system assume know about hook_variables(), which define variables' defaults. But sometimes module not loaded yet! So second parameter still there, but now is option.

The hook_variables hook work like this:

<?php
function hook_variables() {
  return array(
    'name_of_var' => 'default value of var',
  );
}
?>

It also has fallback to deal with variable variables. For exampl, if a variable my_variable_3 not defined, it will look for defined variable my_variable.

It also can do variables that require callback, so as save time!
See:

<?php
function hook_variables() {
  return array(
    array(
      'name' => 'my_var_name',
      'callback' => 'url',
      'arguments' => array(NULL, NULL, NULL, TRUE),
    ),
  );
}
?>

Above will cause url(NULL, NULL, NULL, TRUE) to be called for the default of variable, but will not be executed until acually needed!

So, this do solve google problem after all. I am hoping this patch will be applied soon as possible so we can get google back working in my country. Thank you!