[RFA] Make dwarf2_free_objfile static

[Tom Tromey]

>>>>> "Simon" == Simon Marchi <simon.marchi@polymtl.ca> writes:

>> I don't know if we have a preference for static_cast over C style
>> casting these days?

Simon> Indeed, static_cast provides some compile-time safety, so I guess we
Simon> should always prefer that over the C-style cast.

I made this change.

I think it would be even nicer if the registry functions were type-safe.
I haven't looked into this though.

Tom