This ties libctf into the build system, and makes binutils depend on it
(used by the next commits).
* Makefile.def (host_modules): Add libctf.
* Makefile.def (dependencies): Likewise.
libctf depends on zlib, libiberty, and bfd.
* Makefile.in: Regenerated.
* configure.ac (host_libs): Add libctf.
* configure: Regenerated.
libctf/
* Makefile.am: New.
* Makefile.in: Regenerated.
* config.h.in: Likewise.
* aclocal.m4: Likewise.
* configure: Likewise.
