[infoscanner] don't read into archives when looking for trailers
[infoscanner] don't do a CDirectory::Exists() check when we set a path hash to empty - it's expensive for some VFS filesystems, and it doesn't matter if we add non-existent paths to the database (should SetPathHash ever be called on a non-existent path)
[infoscanner] don't invalidate paths whenever DeleteMovie() is done if all we're doing is updating details in-place
Merge pull request #3956 from jmarshallnz/import_speedups

Video library: Import speedups