Handle discrepancy in file_view_multiple() when called from entity_view()

Problem/Motivation

When called from the Entity API's entity_view(), file_view_multiple() has parameters in an unexpected order. The $langcode parameter is actually the entity type ("file") and the $weight parameter is the true langcode. This means the langcode is lost when files are viewed using entity_view().

Proposed resolution

Rather than change the API's of entity or file_entity, add a simple check for this discrepancy, and fix it.

Remaining tasks

Review the attached patch.

User interface changes

None.

API changes

None.