[patch bfd]: Fix PR ld/12742 for windows targets

[nick clifton]

Hi Kai,

> 2012-03-09  Kai Tietz<ktietz@redhat.com>
>
> 	PR ld/12742
> 	* configure.in (AC_CHECK_HEADERS): Test for windows.h and dlfcn.h.
> 	* plugin.c: Guard include of dlfcn.h if HAVE_DLFCN_H is defined.
> 	Add windows.h header include if HAVE_WINDOWS_H is defined.
> 	(dlerror): New static function if windows variant is used instead
> 	of dlfcn.h.
> 	(dlclose): Likewise.
> 	(dlopen): Likewise.
> 	(dlsym): Likewise.
> 	* configure: Regenerated.
> 	* config.in: Regenerated.

Approved - please apply.

Cheers
   Nick