Optimize CCK harvesting by adding index to media_mover_files table

this makes sense and we were seeing simular results. I also added one for process_file based on this other patch on drupal.org/node/712998

for the function can use either harvest_file or process_file for the select.

Thanks for the patches. Applied to the 6.1.x branch and adapted to 6.2.x

@arthuff: You fixed the 6.x.2.x-dev schema, but you did NOT provide an update_N hook. Although it's a dev and the use is on everybody's own risk you should provide update_n hooks, otherwise we will have inconsistent database versions. I'm going to use this version to build a production site. I know that I'll have to test more but I thought it is OK, now I am in doubt if this would be a good idea.

I see, that there is no update path from 6.x.1.x to 6.x.2.x, for that it might be just ok to leave a message on the modules page. Although, why not provide the update functions now, and do it step by step. Later you will loose track and it makes things more complicate.

* FIX keyname should be 'cid_fid' (not 'cid,fid'), this was not valid and therefore the table media_mover_files could not be created.
* ADD 'not null' => TRUE, 'unsigned' => TRUE to serial fields, as described in http://drupal.org/node/146939 (All fields listed in the primary key must have 'not null' => TRUE in their specification).
* ADD update function media_mover_api_update_6201: Add more indexes to table media_mover_files for better performance.
* CHANGE mmfid is already an index because its a primary key (and does not need to be declared as index again).
* CHANGE consistent code formatting.