gdb: Remove compile-related attributes from struct language

The following patch will add a configure option to disable the compile
subsystem at compilation time. To do that, nearly all code that
interfaces with compile should be confined to the compile sub-folder.

This commit is the first step, removing the compile-related method from
the language struct and adding 2 new functions to compile.c that do the
same job in a slightly different way. Adding things to the language
struct is a more extendable way to add support for languages, but
considering compile is quite bit-rotted and questionably supported, I
don't think it will be extended any time soon, and using ifdefs to
handle disabling compile with configure felt like a messier solution.

There should be no visible changes after this commit.

Approved-By: Tom Tromey <tom@tromey.com>
6 files changed