PR12265, Compiling ld/ fails on Solaris 8

The fail was due to -Werror and headers included by dlfcn.h and
elf-bfd.h disagreeing about AT_DCACHEBSIZE and other AT_*.  Not a
serious problem obviously, since release versions of binutils don't
enable -Werror and the defines are not used.  Anyway, reduce the
number of files that might hit this problem by only including dlfcn.h
where it is needed.

	PR 12265
	* sysdep.h: Don't include dlfcn.h here.
	* plugin.c: Include it here.

ld/plugin.c

@@ -51,7 +51,9 @@
 #if !(defined(errno) || defined(_MSC_VER) && defined(_INC_ERRNO))
 extern int errno;
 #endif
-#if !defined (HAVE_DLFCN_H) && defined (HAVE_WINDOWS_H)
+#if defined (HAVE_DLFCN_H)
+#include <dlfcn.h>
+#elif defined (HAVE_WINDOWS_H)
 #include <windows.h>
 #endif
 

ld/sysdep.h

@@ -61,10 +61,6 @@
 #endif
 #endif
 
-#ifdef HAVE_DLFCN_H
-#include <dlfcn.h>
-#endif
-
 #ifndef O_RDONLY
 #define O_RDONLY 0
 #endif