Perform alterations to a specific block.
Modules can implement hook_block_view_MODULE_DELTA_alter() to modify a specific block, rather than implementing hook_block_view_alter().
$data: The data as returned from the hook_block_view() implementation of the module that defined the block. This could be an empty array or NULL value (if the block is empty) or an array containing:
$block: The block object, as loaded from the database, having the main properties:
Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.
function hook_block_view_MODULE_DELTA_alter(&$data, $block) {
// This code will only run for a specific block. For example, if MODULE_DELTA
// in the function definition above is set to "mymodule_somedelta", the code
// will only run on the "somedelta" block provided by the "mymodule" module.
// Change the title of the "somedelta" block provided by the "mymodule"
// module.
$data['subject'] = t('New title of the block');
}