[Auditor] Remove libtool *.la files

[fingolfin]

Resolves #1104 (or at least will, once it is complete)

TODO:

• add a test (or in general: properly test it)
• document it (where?)
• perhaps the Julia code to another place?

[giordano]

add a test (or in general: properly test it)

To do this it may be easier to move this to a function in the auditor/ directory and add a test for that function only.

A question is: should we have (yet another, sigh) flag to disable this pass if necessary? Audit passes have to be reworked in a saner way, but that's #670.

[fingolfin]

I am going to add an autotools build system to libfoo, then testing this feature is a trivial consequence.

[fingolfin]

I don't really think we need a flag to disable this. We already make sure to not delete files that have extension .la but are not libtool files. And there simply are no legitimate applications of an installed *.la file anymore. Even Autotools Mythbuster agrees: "their presence on most modern systems is vestigial at best". It has a fringe application for static linking (but we don't care about that), and nothing else.

[giordano]

Awesome work, thanks! Only a request about one more test.