maint: don’t include config.h twice

* gl/lib/fadvise.h, gl/lib/smack.h, src/blake2/blake2-impl.h:
Do not include config.h from a .h file.  config.h is supposed
to be included once, at the start of compilation and before
any other file.

gl/lib/fadvise.h

@@ -14,7 +14,6 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
 
-#include <config.h>
 #include <stdio.h>
 #include <fcntl.h>
 #include <sys/types.h>

gl/lib/smack.h

@@ -17,8 +17,6 @@
 /* Here we replace or wrap the most common smack functions used by coreutils.
    Others will need to be protected by HAVE_SMACK.  */
 
-#include <config.h>
-
 #ifdef HAVE_SMACK
 # include <sys/smack.h>
 #else

src/blake2/blake2-impl.h

@@ -15,9 +15,6 @@
 #ifndef BLAKE2_IMPL_H
 #define BLAKE2_IMPL_H
 
-#ifdef HAVE_CONFIG_H
-# include <config.h>
-#endif
 #ifndef WORDS_BIGENDIAN
 # define NATIVE_LITTLE_ENDIAN 1
 #endif