PHP-1226: Add support for the new listIndexes command in 2.7.5

Some of this is also in #741 , which should be merged first.
If retval is not NULL, and php_mongo_trigger_error_on_command_failure returns FAILURE, then retval contains the full error document that comes back from the server, which we return. 

I couldn't come up with a way to make a test case for this, feel free to provide one if you can.