vim-patch:9.0.1963: Configure script may not detect xattr

Problem:  Configure script may not detect xattr correctly
Solution: include sys/xattr instead of attr/xattr,
          make Test_write_with_xattr_support() test
          xattr feature correctly

This also applies to the Smack security feature, so change the include
and configure script for it as well.

closes: vim/vim#13229

6de4e58cf2

src/nvim/os/fs.c

@@ -30,7 +30,7 @@
 #endif
 
 #ifdef HAVE_XATTR
-# include <attr/xattr.h>
+# include <sys/xattr.h>
 # define XATTR_VAL_LEN 1024
 #endif