* libmisc/pwdcheck.c: Do not include <pwd.h>. Include <shadow.h>

and "pwauth.h" only when compiled without PAM support.
* src/chfn.c, src/chsh.c: Do not include <shadow.h>
* lib/commonio.c: Do not include <shadow.h>. Do not include
  <pwd.h>. Include "nscd.h" instead of <nscd.h>.
* configure.in: Do not check if shadow.h exist, but make sure it
  exists.
* libmisc/pwdcheck.c, src/chfn.c, src/chsh.c, lib/defines.h,
  lib/shadowmem.c, lib/shadowio.c, lib/commonio.c:
  HAVE_SHADOW_H is no more needed (shadow.h should always exist).

libmisc/pwdcheck.c

@@ -2,16 +2,14 @@
 
 #ident "$Id$"
 
-#include <pwd.h>
 #include <stdio.h>
 #include "prototypes.h"
 #include "defines.h"
-#include "pwauth.h"
-#ifdef HAVE_SHADOW_H
-#include <shadow.h>
-#endif
 #ifdef USE_PAM
 #include "pam_defs.h"
+#else
+#include <shadow.h>
+#include "pwauth.h"
 #endif
 #define WRONGPWD2	"incorrect password for `%s'"
 void passwd_check (const char *user, const char *passwd, const char *progname)