bootstrap/elements/file.bst: update to 5.35

Hi,

Although those changes look scary, there is nothing to be concerned about:

1. the functions missing are not part of the ABI (and programs should not be using them)
2. the magic_set structure is not exposed in the ABI.

The only thing you need to make sure is that the magic database and the magic library are consistent...

https://mailman.astron.com/pipermail/file/2019-January/000060.html