Converts the bulk of cf_gen to C++ OOP code.

Converts the bulk of cf_gen to C++ OOP code.

* char* tree members to std::string. Which eliminates xstrdup() and
  xis*() calls.

* structs to classes and replaces calloc/free with new/delete.

* link cf_gen_depends.cci directly to autoconf.h defines.

The result of these is that we can erase the dependencies on util.h,
time.cc, config.h, libcompat.la, libmisc.la and other libraries.
Directly fixing seevral build and cross-compile issues that keep appearing
on various OS.

TODO:
 There is a bit further cleanup we can do. Replacing several classes with
 std::list<std::string>.